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Kusakabe, R, Satoh N, Holland LZ, Kusakabe T.  1999.  Genomic organization and evolution of actin genes in the amphioxus Branchiostoma belcheri and Branchiostoma floridae. Gene. 227:1-10.   10.1016/s0378-1119(98)00608-8   AbstractWebsite

We previously described the cDNA. cloning and expression patterns of actin genes from amphioxus Branchiostoma floridae (Kusakabe, R., Kusakabe, T., Satoh, N., Holland, N.D., Holland, L.Z., 1997. Differential gene expression and intracellular mRNA localization of amphioxus actin isoforms throughout development: implications for conserved mechanisms of chordate development. Dev. Genes Evol. 207, 203-215). In the present paper, we report the characterization of cDNA clones for actin genes from a closely related species, Branchiostoma belcheri, and the exon-intron organization of B. floridae actin genes. Each of these two amphioxus species has two types of actin genes, muscle and cytoplasmic. The coding and non-coding regions of each type are well-conserved between the two species. A comparison of nucleotide sequences of muscle actin genes between the two species suggests that a gene conversion may have occurred between two B. floridae muscle actin genes BfMA1 and BfMA2. From the conserved positions of introns between actin genes of amphioxus and those of other deuterostomes, the evolution of deuterostome actin genes can be inferred. Thus, the presence of an intron at codon 328/329 in Vertebrate muscle and cytoplasmic actin genes but not in any known actin gene in other deuterostomes suggests that a gene conversion may have occurred between muscle and cytoplasmic actin genes during the early evolution of the vertebrates after separation from other deuterostomes. A Southern blot analysis of genomic DNA revealed that the amphioxus genome contains multiple muscle and cytoplasmic actin genes. Some of these actin genes seem to have arisen from recent duplication and gene conversion. Our findings suggest that the multiple genes encoding muscle and cytoplasmic actin isoforms arose independently in each of the three chordate lineages and that gene duplications and gene conversions established the extant actin multigene family during the evolution of chordates. (C) 1999 Elsevier Science B.V. All rights reserved.

Holland, LZ.  2015.  Genomics, evolution and development of amphioxus and tunicates: The Goldilocks principle. Journal of Experimental Zoology Part B-Molecular and Developmental Evolution. 324:342-352.   10.1002/jez.b.22569   AbstractWebsite

Morphological comparisons among extant animals have long been used to infer their long-extinct ancestors for which the fossil record is poor or non-existent. For evolution of the vertebrates, the comparison has typically involved amphioxus and vertebrates. Both groups are evolving relatively slowly, and their genomes share a high level of synteny. Both vertebrates and amphioxus have regulative development in which cell fates become fixed only gradually during embryogenesis. Thus, their development fits a modified hourglass model in which constraints are greatest at the phylotypic stage (i.e., the late neurula/early larva), but are somewhat greater on earlier development than on later development. In contrast, the third group of chordates, the tunicates, which are sister group to vertebrates, are evolving rapidly. Constraints on evolution of tunicate genomes are relaxed, and they have discarded key developmental genes and organized much of their coding sequences into operons, which are transcribed as a single mRNA that undergoes trans-splicing. This contrasts with vertebrates and amphioxus, whose genomes are not organized into operons. Concomitantly, tunicates have switched to determinant development with very early fixation of cell fates. Thus, tunicate development more closely fits a progressive divergence model (shaped more like a wine glass than an hourglass) in which the constraints on the zygote and very early development are greatest. This model can help explain why tunicate body plans are so very diverse. The relaxed constraints on development after early cleavage stages are correlated with relaxed constraints on genome evolution. The question remains: which came first? J. Exp. Zool. (Mol. Dev. Evol.) 324B: 342-352, 2015. (c) 2014 Wiley Periodicals, Inc.

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Holland, LZ.  2002.  Heads or tails? Amphioxus and the evolution of anterior-posterior patterning in deuterostomes Developmental Biology. 241:209-228.   10.1006/dbio.2001.0503   AbstractWebsite

In Xenopus, the canonical Wnt-signaling pathway acting through (beta-catenin functions both in establishing the dorso-ventral axis and in patterning the anterior-posterior axis. This pathway also acts in patterning the animal-vegetal axis in sea urchins. However, because sea urchin development is typically indirect, and adult sea urchins have pentamerous symmetry and lack a longitudinal nerve cord, it has not been clear how the roles of the canonical Wnt-signaling pathway in axial patterning in sea urchins and vertebrates are evolutionarily related. The developmental expression patterns of Notch, brachyury, caudal, and eight Wnt genes have now been determined for the invertebrate chordate amphioxus, which, like sea urchins, has an early embryo that gastrulates by invagination, but like vertebrates, has a later embryo with a dorsal hollow nerve cord that elongates posteriorly from a tail bud. Comparisons of amphioxus with other deuterostomes suggest that patterning of the ancestral deuterostome embryo along its anterior-posterior axis during the late blastula and subsequent stages involved a posterior signaling center including Writs, Notch, and transcription factors such as brachyury and caudal. In tunicate embryos, in which cell numbers are reduced and cell fates largely determined during cleavage stages, only vestiges of this signaling center are still apparent; these include localization of Wnt-5 mRNA to the posterior cytoplasm shortly after fertilization and localization of beta-catenin to vegetal nuclei during cleavage stages. Neither in tunicates nor in amphioxus is there any evidence that the canonical Wnt-signaling pathway functions in establishment of the dorso-ventral axis. Thus, roles for Wnt-signaling in dorso-ventral patterning of embryos may be a vertebrate innovation that arose in connection with the evolution of yolky eggs and gastrulation by extensive involution. (C) 2001 Elsevier Science.

Fujimura, Y, Titani K, Holland LZ, Roberts JR, Kostel P, Ruggeri ZM, Zimmerman TS.  1987.  A Heparin-Binding Domain of Human Vonwillebrand-Factor - Characterization and Localization to a Tryptic Fragment Extending from Amino-Acid Residue Val-449 to Lys-728. Journal of Biological Chemistry. 262:1734-1739.Website
Holland, ND, Holland LZ.  1991.  The Histochemistry and Fine-Structure of the Nutritional Reserves in the Fin Rays of a Lancelet, Branchiostoma-Lanceolatum (Cephalochordata = Acrania). Acta Zoologica. 72:203-207. AbstractWebsite

Adults of the European lancelet were collected at Banyuls-sur-Mer (Mediterranean France) in mid-spring, shortly before the onset of the breeding season. The dorsal and ventral fin rays were studied by light microscopic histochemistry and by transmission electron microscopy (TEM). Each fin ray is a mass of extracellular material that accumulates beneath the mesothelium of a fin box coelom. The fin ray material is rich in lipids, proteins, and neutral mucopolysaccharides. TEM reveals no lipid droplets in this material. which consists entirely of a packed mass of 15-20 nm granules of medium electron density. It is likely that these granules consist of glycoproteins or glycolipoproteins. Our results are consistent with the proposal of Azariah (1965, Journal of the Marine Biological Association of India 7: 459-661 ) that lancelet fin rays are nutritional reserves supporting gametogenesis during the breeding season.

Fulcher, CA, Roberts JR, Holland LZ, Zimmerman TS.  1985.  Human Factor-Viii Procoagulant Protein - Monoclonal-Antibodies Define Precursor-Product Relationships and Functional Epitopes. Journal of Clinical Investigation. 76:117-124.   10.1172/jci111933   Website
Holland, ND, Holland LZ, Heimberg A.  2015.  Hybrids between the Florida amphioxus (Branchiostoma floridae) and the Bahamas lancelet (Asymmetron lucayanum): Developmental morphology and chromosome counts. Biological Bulletin. 228:13-24. AbstractWebsite

The cephalochordate genera Branchiostoma and Asymmetron diverged during the Mesozoic Era. In spite of the long separation of the parental clades, eggs of the Florida amphioxus, B. floridae, when fertilized with sperm of the Bahamas lancelet, A. lucayanum (and vice versa), develop through embryonic and larval stages. The larvae reach the chordate phylotypic stage (i.e., the pharyngula), characterized by a dorsal nerve cord, notochord, perforate pharynx, and segmented trunk musculature. After about 2 weeks of larval development, the hybrids die, as do the A. lucayanum purebreds, although all were eating the same algal diet that sustains B. floridae purebreds through adulthood in the laboratory; it is thus unclear whether death of the hybrids results from incompatible parental genomes or an inadequate diet. The diploid chromosome count in A. lucayanum and B. floridae purebreds is, respectively, 34 and 38, whereas it is 36 in hybrids in either direction. The hybrid larvae exhibit several morphological characters intermediate between those of the parents, including the size of the preoral ciliated pit and the angles of deflection of the gill slits and anus from the ventral midline. Based on the time since the two parent clades diverged (120 or 160 million years, respectively, by nuclear and mitochondrial gene analysis), the cross between Branchiostoma and Asymmetron is the most extreme example of hybridization that has ever been unequivocally demonstrated among multicellular animals.

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Holland, LZ, Sower SA.  2010.  "Insights of Early Chordate Genomics: Endocrinology and Development in Amphioxus, Tunicates and Lampreys": Introduction to the symposium. Integrative and Comparative Biology. 50:17-21.   10.1093/icb/icq039   AbstractWebsite

This symposium focused on the evolution of chordate genomes, in particular, those events that occurred before the appearance of jawed vertebrates. The aim was to highlight insights that have come from the genome sequences of jawless chordates (lampreys, tunicates, and amphioxus) not only into evolution of chordate genomes, but also into the evolution of the organism. To this end, we brought together researchers whose recent work on these organisms spans the gap from genomics to the evolution of body forms and functions as exemplified by endocrine systems and embryonic development.

Boldrin, F, Martinucci G, Holland LZ, Miller RL, Burighel P.  2009.  Internal fertilization in the salp Thalia democratica. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 87:928-940.   10.1139/z09-083   AbstractWebsite

Among tunicates, gamete morphology and sperm-egg interactions have been extensively investigated in ascidians, and to a lesser extent in appendicularians and thaliaceans. Sperm-egg interaction has been studied in only one salp, Pegea socia (Bosc, 1802). To determine if the pattern of internal fertilization of P. socia is generally applicable to salps, we performed an ultrastructural study on blastozooids of Thalia democratica (Forsskal, 1775). The ovary, located in the mantle near the gut, consists of a single oocyte connected to the atrial chamber wall by a "fertilization duct", resembling a stack of single cells without a lumen. The flagellate sperm has a long corkscrew-like head with the single mitochondrion twisted around the nucleus. Fertilization is internal, and sperm actively penetrate the atrial wall and bore through the cells of the fertilization duct. During this process, the fertilization duct shortens as the cells move apart, one to one side and the next to the other, and rejoin to form a central lumen, which contains many sperm. At the same time a few sperm reach the periovular space for fertilizing the oocyte. Comparisons with P. socia indicate that this singular mode of internal fertilization with a complex corkscrew sperm actively penetrating the fertilization duct cells, probably evolved in the salp ancestor and has been modified to some extent in various genera.

Jaffe, LA, Gould-Somero M, Holland LZ.  1979.  Ionic Mechanism of the Fertilization Potential of the Marine Worm, Urechis caupo (Echiura) . Journal of General Physiology . 73(4):469-492.   10.1085/jgp.73.4.469  
Pareti, FI, Fujimura Y, Dent JA, Holland LZ, Zimmerman TS, Ruggeri ZM.  1986.  Isolation and Characterization of a Collagen Binding Domain in Human Vonwillebrand-Factor. Journal of Biological Chemistry. 261:5310-5315.Website
Glardon, S, Holland LZ, Gehring WJ, Holland ND.  1998.  Isolation and developmental expression of the amphioxus Pax-6 gene (AmphiPax-6): insights into eye and photoreceptor evolution. Development. 125:2701-2710. AbstractWebsite

Pax-6 genes have been identified from a broad range of invertebrate and vertebrate animals and shown to be always involved in early eye development. Therefore, it has been proposed that the various types of eyes evolved from a single eye prototype, by a Pax-6-dependent mechanism. Here we describe the characterization of a cephalochordate Pax-6 gene. The single amphioxus Pax-6 gene (AmphiPax-6) can produce several alternatively spliced transcripts, resulting in proteins with markedly different amino and carboxy termini, The amphioxus Pax-6 proteins are 92% identical to mammalian Pax-6 proteins in the paired domain and 100% identical in the homeodomain. Expression of AmphiPax-6 in the anterior epidermis of embryos may be related to development of an olfactory epithelium. Expression is also detectable in Hatschek's left diverticulum as it forms the preoral ciliated pit, part of which gives rise to the homolog of the vertebrate anterior pituitary, A zone of expression in the anterior neural plate of early embryos is carried into the cerebral vesicle (a probable diencephalic homolog) during neurulation, This zone includes cells that will differentiate into the lamellar body, a presumed homolog of the vertebrate pineal eye, In neurulae, AmphiPax-6 is also expressed in ventral cells at the anterior tip of the nerve cord; these cells are precursors of the photoreceptive neurons of the frontal eye, the presumed homolog of the vertebrate paired eyes. However, AmphiPax-6 expression was not detected in two additional types of photoreceptors, the Joseph cells or the organs of Hesse, which are evidently relatively recent adaptations (ganglionic photoreceptors) and appear to be rare exceptions to the general rule that animal photoreceptors develop from a genetic program triggered by Pax-6.

Cross, NL, Slezynger TC, Holland LZ.  1985.  Isolation and Partial Characterization of Urechis-Caupo Egg Envelopes. Journal of Cell Science. 74:193-205.Website
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Holland, ND, Holland LZ.  2010.  Laboratory Spawning and Development of the Bahama Lancelet, Asymmetron lucayanum (Cephalochordata): Fertilization Through Feeding Larvae. Biological Bulletin. 219:132-141. AbstractWebsite

Here we report on spawning and development of the Bahama lancelet, Asymmetron lucayanum. Ripe adults collected in Bimini spawned the same evening when placed in the dark for 90 minutes. The developmental morphology is described from whole mounts and histological sections. A comparison between development in A symmetron and the better known cephalochordate genus Branchiostoma reveals similarities during the early embryonic stages but deviations by the late embryonic and early larval stages. Thus, the initial positions of the mouth, first gill slit, and anus differ between the two genera. Even more strikingly, Hatschek's right and left diverticula, which arise by enterocoely at the anterior end of the pharynx in Branchiostoma, never form during Asymmetron development. In Branchiostoma, these diverticula become the rostral coelom and preoral pit. In Asymmetron, by contrast, homologs of the rostral coelom and preoral pit form by schizocoely within an anterior cell cluster of unproven (but likely endodermal) origin. Proposing evolutionary scenarios to account for developmental differences between Asymmetron and Branchiostoma is currently hampered by uncertainty over which genus is basal in the cephalochordates. A better understanding of developmental diversity within the cephalochordates will require phylogenetic analyses based on nuclear genes and the genome sequence of an Asymmetron species.

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Holland, LZ, Miller RL.  1994.  Mechanism of Internal Fertilization in Pegea-Socia (Tunicata, Thaliacea), a Salp with a Solid Oviduct. Journal of Morphology. 219:257-267.   10.1002/jmor.1052190305   AbstractWebsite

The ovary of the salp Pegea socia (Bose, 1802) is located at the end of an atrial diverticulum. The ovary consists of a single oocyte encased in a layer of follicle cells and is connected to the atrial epithelium by an oviduct. Transmission electron microscopy shows that the oocyte lacks a vitelline layer, cortical granules, and yolk granules and that the oviduct lacks a continuous lumen. What previous authors thought was a lumen is a line of dense intercellular junctions running down the center of the oviduct. The sperm nucleus in this species, as in other salps, is elongate. The tubular mitochondrion spirals about the sperm nucleus giving it a corkscrew-shape appearance. Sperm reach the ovary when the oocyte is still at the germinal vesicle stage. Many sperm swim up the atrial diverticulum and burrow through the cells of the atrial epithelium, oviduct, and follicular epithelium. Thus oviduct shortening, which occurs when the oocyte is in the meiotic divisions, is evidently unrelated to sperm moving up the oviduct. All previous authors, who argued either that a continuous lumen is necessary for sperm to move up the oviduct or that sperm bypass the oviduct, were incorrect. (C) 1994 Wiley-Liss, Inc.

Holland, PWH, Garcia-Fernandez J, Holland LZ, Williams NA, Holland ND.  1994.  The Molecular Control of Spatial Patterning in Amphioxus. Journal of the Marine Biological Association of the United Kingdom. 74:49-60. AbstractWebsite

The embryology of amphioxus (Chordata: Cephalochordata) has features in common with vertebrate embryology, reflecting a dose phylogenetic relationship between the two taxa. Amphioxus differs from vertebrates, however, in having less complex organogenesis and cranial morphogenesis, and less specialization along the anteroposterior body axis. Here we illustrate this by describing the embryology of an amphioxus species, Branchiostoma floridae. To gain further insight into the origins, evolutionary divergence and comparative embryology of these taxa, we are comparing the molecular control of embryonic development in amphioxus and vertebrates. For these analyses, we are focusing on homeobox genes: a diverse multigene family implicated in developmental control in many Metazoa. We report the results of PCR-based experiments which reveal that the amphioxus genome has homeobox genes from several recognized gene classes. The PCR experiments also suggest that amphioxus has fewer 'Hox' and 'Msx' class homeobox genes than do vertebrates. We suggest, therefore, that amphioxus may be a living descendant from an intermediate stage in the evolution of homeobox gene family complexity, and the complexity of vertebrate developmental control. The pattern of gene expression during embryogenesis has been described for one amphioxus homeobox gene of the Hox class. This gene is primarily expressed in the presumptive neural tube of amphioxus neurulae, later embryos and larvae, in a spatially-restricted manner. The expression data lead us to suggest that Hox genes are involved in the control of spatial patterning in the neural tube of amphioxus; the data are also interpreted as giving insight into possible homology between the amphioxus and vertebrate body plans.

Holland, LZ.  1996.  Muscle development in amphioxus: Morphology, biochemistry, and molecular biology. Israel Journal of Zoology. 42:S235-S246. AbstractWebsite

This review concerns the structure and biochemistry of muscle in amphioxus. Most work has focused on the segmented swimming (axial) muscles. These muscles derive from the medial wall of the somites, which arise as evaginations from the gut wall. The myotomal muscle cells of amphioxus, unlike those of vertebrates, never fuse, but remain mononucleate, contain only one myofibril, and span the entire length of the myotome. The muscle cells are very thin and lack a T-tubule system. There are two, maybe three, types of fibers. Innervation is via muscle tails, which contact the basal lamina of the nerve cord. The notochord is also composed of striated muscle cells, which similarly send muscle tails to the nerve cord. Less is known about the biochemistry of muscle. The notochord, like molluskan catch muscle, contains paramyosin. Among the muscle-specific proteins sequenced are alkali myosin light chain, troponin C and sarcoplasmic calcium-binding proteins, calcium-vector protein, and its target protein calcium vector-target protein. The only muscle regulatory factors identified are two MyoD proteins. Almost nothing is known about muscle enzymes in amphioxus.

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Escriva, H, Bertrand S, Germain P, Robinson-Rechavi M, Umbhauer M, Cartry J, Duffraisse M, Holland L, Gronemeyer H, Laudet V.  2006.  Neofunctionalization in vertebrates: The example of retinoic acid receptors. Plos Genetics. 2:955-965.   10.1371/journal.pgen.0020102   AbstractWebsite

Understanding the role of gene duplications in establishing vertebrate innovations is one of the main challenges of Evo-Devo (evolution of development) studies. Data on evolutionary changes in gene expression (i.e., evolution of transcription factor-cis-regulatory elements relationships) tell only part of the story; protein function, best studied by biochemical and functional assays, can also change. In this study, we have investigated how gene duplication has affected both the expression and the ligand-binding specificity of retinoic acid receptors (RARs), which play a major role in chordate embryonic development. Mammals have three paralogous RAR genes-RAR alpha, beta, and gamma-which resulted from genome duplications at the origin of vertebrates. By using pharmacological ligands selective for specific paralogues, we have studied the ligand-binding capacities of RARs from diverse chordates species. We have found that RAR beta-like binding selectivity is a synapomorphy of all chordate RARs, including a reconstructed synthetic RAR representing the receptor present in the ancestor of chordates. Moreover, comparison of expression patterns of the cephalochordate amphioxus and the vertebrates suggests that, of all the RARs, RAR beta expression has remained most similar to that of the ancestral RAR. On the basis of these results together, we suggest that while RAR beta kept the ancestral RAR role, RAR alpha and RAR gamma diverged both in ligand-binding capacity and in expression patterns. We thus suggest that neofunctionalization occurred at both the expression and the functional levels to shape RAR roles during development in vertebrates.

Holland, LZ, Ocampo Daza D.  2018.  A new look at an old question: when did the second whole genome duplication occur in vertebrate evolution? Genome Biology. 19   10.1186/s13059-018-1592-0   AbstractWebsite

A recent study used 61 extant animal genomes to reconstruct the chromosomes of the hypothetical amniote ancestor. Comparison of this karyotype to the 17 chordate linkage groups previously inferred in the ancestral chordate indicated that two whole genome duplications probably occurred in the lineage preceding the ancestral vertebrate.

Ono, H, Koop D, Holland LZ.  2018.  Nodal and Hedgehog synergize in gill slit formation during development of the cephalochordate Branchiostoma floridae. Development. 145   10.1242/dev.162586   AbstractWebsite

The larval pharynx of the cephalochordate Branchiostoma (amphioxus) is asymmetrical. The mouth is on the left, and endostyle and gill slits are on the right. At the neurula, Nodal and Hedgehog (Hh) expression becomes restricted to the left. To dissect their respective roles in gill slit formation, we inhibited each pathway separately for 20 min at intervals during the neurula stage, before gill slits penetrate, and monitored the effects on morphology and expression of pharyngeal markers. The results pinpoint the short interval spanning the gastrula/neurula transition as the critical period for specification and positioning of future gill slits. Thus, reduced Nodal signaling shifts the gill slits ventrally, skews the pharyngeal domains of Hh, Pax1/9, Pax2/5/8, Six1/2 and IrxC towards the left, and reduces Hh and Tbx1/10 expression in endoderm and mesoderm, respectively. Nodal auto-regulates. Decreased Hh signaling does not affect gill slit positions or Hh or Nodal expression, but it does reduce the domain of Gli, the Hh target, in the pharyngeal endoderm. Thus, during the neurula stage, Nodal and Hh cooperate in gill slit development - Hh mediates gill slit formation and Nodal establishes their left-right position.

Holland, LZ.  2005.  Non-neural ectoderm is really neural: Evolution of developmental patterning mechanisms in the non-neural ectoderm of chordates and the problem of sensory cell homologies. Journal of Experimental Zoology Part B-Molecular and Developmental Evolution. 304B:304-323.   10.1002/jez.21038   AbstractWebsite

In chordates, the ectoderm is divided into the neuroectoderm and the so-called non-neural ectoderm. In spite of its name, however, the non-neural ectoderm contains. numerous sensory cells. Therefore, the term "non-neural" ectoderm should be replaced by "general ectoderm." At least in amphioxus and tunicates and possibly in vertebrates as well, both the neuroectoderm and the general ectoderm are patterned anterior/posteriorly by mechanisms involving retinoic acid and Hox genes. In amphioxus and tunicates the ectodermal sensory cells, which have a wide range of ciliary and microvillar configurations, are mostly primary neurons sending axons to the CNS, although a minority lack axons. In contrast, vertebrate mechanosensory cells, called hair cells, are all secondary neurons that lack axons and have a characteristic eccentric cilium adjacent to a group of microvilli of graded lengths. It has been highly controversial whether the ectodermal sensory cells in the oral siphons of adult tunicates are homologous to vertebrate hair cells. In some species of tunicates, these cells appear to be secondary neurons, and microvillar and ciliary configurations of some of these cells approach those of vertebrate hair cells. However, none of the tunicate cells has all the characteristics of a hair cell, and there is a high degree of variation among ectodermal sensory cells within and between different species. Thus, similarities between the ectodermal sensory cells of any one species of tunicate and craniate hair cells may well represent convergent evolution rather than homology.

Striedter, GF, Belgard TG, Chen CC, Davis FP, Finlay BL, Gunturkun O, Hale ME, Harris JA, Hecht EE, Hof PR, Hofmann HA, Holland LZ, Iwaniuk AN, Jarvis ED, Karten HJ, Katz PS, Kristan WB, Macagno ER, Mitra PP, Moroz LL, Preuss TM, Ragsdale CW, Sherwood CC, Stevens CF, Stuttgen MC, Tsumoto T, Wilczynski W.  2014.  NSF workshop report: Discovering general principles of nervous system organization by comparing brain maps across species. Journal of Comparative Neurology. 522:1445-1453.   10.1002/cne.23568   AbstractWebsite

Efforts to understand nervous system structure and function have received new impetus from the federal Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative. Comparative analyses can contribute to this effort by leading to the discovery of general principles of neural circuit design, information processing, and gene-structure-function relationships that are not apparent from studies on single species. We here propose to extend the comparative approach to nervous system maps' comprising molecular, anatomical, and physiological data. This research will identify which neural features are likely to generalize across species, and which are unlikely to be broadly conserved. It will also suggest causal relationships between genes, development, adult anatomy, physiology, and, ultimately, behavior. These causal hypotheses can then be tested experimentally. Finally, insights from comparative research can inspire and guide technological development. To promote this research agenda, we recommend that teams of investigators coalesce around specific research questions and select a set of reference species' to anchor their comparative analyses. These reference species should be chosen not just for practical advantages, but also with regard for their phylogenetic position, behavioral repertoire, well-annotated genome, or other strategic reasons. We envision that the nervous systems of these reference species will be mapped in more detail than those of other species. The collected data may range from the molecular to the behavioral, depending on the research question. To integrate across levels of analysis and across species, standards for data collection, annotation, archiving, and distribution must be developed and respected. To that end, it will help to form networks or consortia of researchers and centers for science, technology, and education that focus on organized data collection, distribution, and training. These activities could be supported, at least in part, through existing mechanisms at NSF, NIH, and other agencies. It will also be important to develop new integrated software and database systems for cross-species data analyses. Multidisciplinary efforts to develop such analytical tools should be supported financially. Finally, training opportunities should be created to stimulate multidisciplinary, integrative research into brain structure, function, and evolution. J. Comp. Neurol. 522:1445-1453, 2014. (c) 2014 Wiley Periodicals, Inc.

Holland, LZ, Panfilio KA, Chastain R, Schubert M, Holland ND.  2005.  Nuclear beta-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos. Developmental Dynamics. 233:1430-1443.   10.1002/dvdy.20473   AbstractWebsite

In vertebrate development, Wnt/beta-catenin signaling has an early role in specification of dorsal/anterior identity and a late one in posterior specification. To understand the evolution of these roles, we cloned beta-catenin from the invertebrate chordate amphioxus. The exon/intron organization of beta-catenin is highly conserved between amphioxus and other animals including a cnidarian, but not Drosophila. In development, amphioxus P-catenin is concentrated in all nuclei from the 16-cell stage until the onset of gastrulation when it becomes undetectable in presumptive mesendoderm. Li+, which up-regulates Wnt/beta-catenin signaling, had no detectable effect on axial patterning when applied before the late blastula stage, suggesting that a role for P-catenin in specification of dorsal/anterior identity may be a vertebrate innovation. From the mid-gastrula through the neurula stage, the highest levels of nuclear R-catenin are around the blastopore. In the early neurula, P-catenin is down-regulated in the neural plate, but remains high in adjacent non-neural ectoderm. Embryos treated with Li+ at the late blastula stage are markedly posteriorized and lack a neural plate. These results suggest that in amphioxus, as in vertebrates, downregulation of Wnt/beta-catenin signaling in the neural plate is necessary for maintenance of the neuroectoderm and that a major evolutionarily conserved role of Wnt/beta-catenin signaling is to specify posterior identity and pattern the anterior/posterior axis. (c) 2005 Wiley-Liss, Inc.

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Gould-Somero, M, Holland LZ.  1975.  Oocyte differentiation in Urechis caupo (Echiura)-- A Fine-structural Study. Journal of Morphology . 147(4):475-505.   10.1002/jmor.1051470407