Biology subjects

Muhl, V.

Publications and source records attributed to Muhl, V..

2 recordsLinked to original sources

bioRxiv2024

Tissue-specific transcriptomics uncovers novel craniofacial genes underlying jaw divergence in specialist pupfishes

The regulation of gene expression is one of the key evolutionary processes driving phenotypic divergence among species. Here, we investigate the tissue-specific gene expression of a non-model adaptive radiation of Cyprinodon pupfishes, characterized by their divergent dietary niches and exceptionally fast rates of craniofacial evolution. By comparing tissue-specific gene expression in the most morphologically divergent skeletal structure, the oral jaws, with the relatively morphologically conserved caudal tail region, we identified genes that were differentially expressed exclusively in the developing jaws of each of the three trophic specialists at hatching (8 dpf) and not in any other species. We then assessed their overlap (as transcriptionally-regulated genes) with adaptive regulatory variants identified in previous genomic studies. Our analysis identified pycr3 and atp8a1 as the most promising for craniofacial evolution in the scale-eaters, both genes with no known previous craniofacial function. We functionally confirmed the craniofacial expression of these genes by in situ mRNA hybridization chain reaction and demonstrated their species-specific expression in branchial and muscle tissues between sister species of this young radiation. Our work underscores the power of integrating tissue-specific transcriptomics with speciation genomics to identify novel craniofacial candidate genes controlling divergent morphogenesis in a natural evolutionary mutant system.

developmental biology↗

bioRxiv2023

Discovery of a new craniofacial gene influencing adaptive phenotypes in a non-model pupfish radiation

Understanding the genetic basis of novel adaptations in new species is a fundamental question in biology that also provides an opportunity to uncover new genes and regulatory networks with potential clinical relevance. Here we demonstrate a new role for galr2 in vertebrate craniofacial development using an adaptive radiation of trophic specialist pupfishes endemic to San Salvador Island in the Bahamas. We confirmed the loss of a putative Sry transcription factor binding site in the upstream region of galr2 in scale-eating pupfish and found significant spatial differences in galr2 expression among pupfish species in Meckels cartilage and premaxilla using in situ hybridization chain reaction (HCR). We then experimentally demonstrated a novel function for Galr2 in craniofacial development and jaw elongation by exposing embryos to drugs that inhibit Galr2 activity. Galr2-inhibition reduced Meckels cartilage length and increased chondrocyte density in both trophic specialists but not in the generalist genetic background. We propose a mechanism for jaw elongation in scale-eaters based on the reduced expression of galr2 due to the loss of a putative Sry binding site. Fewer Galr2 receptors in the scale-eater Meckels cartilage may result in their enlarged jaw lengths as adults by limiting opportunities for a postulated Galr2 agonist to bind to these receptors during development. Our findings illustrate the growing utility of linking candidate adaptive SNPs in non-model systems with highly divergent phenotypes to novel vertebrate gene functions.

developmental biology↗