Self-organized patterning of crocodile head scales by compressive folding.

Amniote integumentary appendages constitute a diverse group of micro-organs, including feathers, hair and scales. These structures typically develop as genetically controlled units, the spatial patterning of which emerges from a self-organized chemical Turing system with integrated mechanical feedback. The seemingly purely mechanical patterning of polygonal crocodile head scales provides an exception to this paradigm.

Spontaneous regeneration of cholecystokinergic reticulospinal axons after a complete spinal cord injury in sea lampreys.

In contrast to humans, lampreys spontaneously recover their swimming capacity after a complete spinal cord injury (SCI). This recovery process involves the regeneration of descending axons. Spontaneous axon regeneration in lampreys has been mainly studied in giant descending neurons.

A lamprey neural cell type atlas illuminates the origins of the vertebrate brain.

The vertebrate brain emerged more than ~500 million years ago in common evolutionary ancestors. To systematically trace its cellular and molecular origins, we established a spatially resolved cell type atlas of the entire brain of the sea lamprey-a jawless species whose phylogenetic position affords the reconstruction of ancestral vertebrate traits-based on extensive single-cell RNA-seq and in situ sequencing data. Comparisons of this atlas to neural data from the mouse and other jawed vertebrates unveiled various shared features that enabled the reconstruction of cell types, tissue structures and gene expression programs of the ancestral vertebrate brain.

Full regeneration of descending corticotropin-releasing hormone axons after a complete spinal cord injury in lampreys.

Sea lampreys are a vertebrate model of interest for the study of spontaneous axon regeneration after spinal cord injury (SCI). Axon regeneration research in lampreys has focused on the study of giant descending neurons, but less so on neurochemically-distinct descending neuronal populations with small caliber axons. Corticotropin-releasing hormone (CRH) is a neuropeptide that regulates the stress response or locomotion.

Roles of dual specificity tyrosine-phosphorylation-regulated kinase 2 in nervous system development and disease.

Dual specificity tyrosine-phosphorylation-regulated kinases (DYRKs) are a group of conserved eukaryotic kinases phosphorylating tyrosine, serine, and threonine residues. The human DYRK family comprises 5 members (DYRK1A, DYRK1B, DYRK2, DYRK3, and DYRK4). The different DYRKs have been implicated in neurological diseases, cancer, and virus infection.

Developmental genoarchitectonics as a key tool to interpret the mature anatomy of the chondrichthyan hypothalamus according to the prosomeric model.

The hypothalamus is a key vertebrate brain region involved in survival and physiological functions. Understanding hypothalamic organization and evolution is important to deciphering many aspects of vertebrate biology. Recent comparative studies based on gene expression patterns have proposed the existence of hypothalamic histogenetic domains (paraventricular, TPa/PPa; subparaventricular, TSPa/PSPa; tuberal, Tu/RTu; perimamillary, PM/PRM; and mamillary, MM/RM), revealing conserved evolutionary trends.

Identifying Amygdala-Like Territories in Scyliorhinus canicula (Chondrichthyan): Evidence for a Pallial Amygdala.

To identify the putative amygdalar complex in cartilaginous fishes, our first step was to obtain evidence that supports the existence of a pallial amygdala in the catshark Scyliorhinus canicula, at present the prevailing chondrichthyan model in comparative neurobiology and developmental biology. To this end, we analyzed the organization of the lateral walls of the telencephalic hemispheres of adults, juveniles, and early prehatching embryos by immunohistochemistry against tyrosine hydroxylase (TH), somatostatin (SOM), Pax6, serotonin (5HT), substance P (SP), and Met-enkephalin (MetEnk), calbindin-28k (CB), and calretinin (CR), and by in situ hybridization against regulatory genes such as Tbr1, Lhx9, Emx1, and Dlx2. Our data were integrated with those available from the literature related to the secondary olfactory projections in this shark species.

The Shark Basal Hypothalamus: Molecular Prosomeric Subdivisions and Evolutionary Trends.

The hypothalamus is a key integrative center of the vertebrate brain. To better understand its ancestral morphological organization and evolution, we previously analyzed the segmental organization of alar subdivisions in the catshark , a cartilaginous fish and thus a basal representative of gnathostomes (jawed vertebrates). With the same aim, we deepen here in the segmental organization of the catshark basal hypothalamus by revisiting previous data on expression and Shh immunoreactivity jointly with new data on expression and proliferating cell nuclear antigen (PCNA) immunoreactivity.

The Shark Alar Hypothalamus: Molecular Characterization of Prosomeric Subdivisions and Evolutionary Trends.

The hypothalamus is an important physiologic center of the vertebrate brain involved in the elaboration of individual and species survival responses. To better understand the ancestral organization of the alar hypothalamus we revisit previous data on , , , 1 expression and Pax6 immunoreactivity jointly with new data on , , , and expression, in addition to immunoreactivity to serotonin (5-HT) and doublecortin (DCX) in the catshark , a key species for this purpose since cartilaginous fishes are basal representatives of gnathostomes (jawed vertebrates). Our study revealed a complex genoarchitecture for the chondrichthyan alar hypothalamus.

Prosomeric organization of the hypothalamus in an elasmobranch, the catshark Scyliorhinus canicula.

The hypothalamus has been a central topic in neuroanatomy because of its important physiological functions, but its mature organization remains elusive. Deciphering its embryonic and adult organization is crucial in an evolutionary approach of the organization of the vertebrate forebrain. Here we studied the molecular organization of the hypothalamus and neighboring telencephalic domains in a cartilaginous fish, the catshark, Scyliorhinus canicula, focusing on ScFoxg1a, ScShh, ScNkx2.