Biology subjects

Dann, J. B.

Publications and source records attributed to Dann, J. B..

2 recordsLinked to original sources

bioRxiv2024

Evolution of the Jawed Vertebrate (Gnathostomata) Stomach through Gene Repertoire Loss: Findings from Agastric Species

Independent and convergent gene loss, such as the loss of gastric enzymes (Pga, Pgc) and proton pump subunits (Atp4a, Atp4b) in monotremes and polyphyletic teleost species have been associated with the agastric phenotype - stomachs lacking gross morphology, gastric glands and acid secretion. The loss of the key gastric hormone gastrin (Gast) has been observed in monotremes, but not corroborated in agastric teleosts. Furthermore, it is unclear how this loss affects the evolution and selection of the native receptor (Cckbr), gastrin releasing peptide (Grp) and receptor (Grpr), or if there are further gene losses associated with the agastric phenotype. We investigated the evolution, selection and conservation of the gastrin physiological pathway and novel gastric genes in a broad range of gastric and agastric vertebrates. Our analyses showed no correlation between the losses of Gast and Grpr with the agastric phenotype in vertebrate lineages. We identified genes implicated in gastric mucosal maintenance and development (Gkn1, Gkn2, Tff1, Tff2, Vsig1, Anxa10) that are lost in agastric species except the echidna, which retained some of them (Gkn1, Tff2, Vsig1). Our findings demonstrate a convergent repertoire of gastric genes lost in agastric species, partial retention of gastric functionality in the echidna, and the diversified roles of gastrin pathway constituents in vertebrate lineages.

evolutionary biology↗

bioRxiv2024

Pseudogenisation of NK3 Homeobox 2 (Nkx3.2) in Monotremes Provides Insight into Unique Gastric Anatomy and Physiology

Development of the vertebrate antral stomach and pyloric sphincter (antropyloric region) - involved in enzymatic breakdown and thoroughfare of food - is underpinned by a highly conserved developmental pathway involving the hedgehog, bone morphogenetic protein (BMP) and Wingless/Int-1 (Wnt) protein families. Monotremes are a unique lineage where acid-based digestion has been lost, and this correlates with a lack of genes for gastric acid and enzymes in the genomes of the platypus (Ornithorhynchus anatinus) and short-beaked echidna (Tachyglossus aculeatus). Furthermore, these species feature unique gastric phenotypes, both with truncated and aglandular antral stomachs and the platypus with no pylorus. Here, we explore the genetic underpinning of monotreme gastric phenotypes, investigating genes important in antropyloric development using the newest monotreme genome sequences (mOrnAna1.pri.v4 and mTacAcu1) together with RNA-seq data. We found that the pathway is generally conserved but, NK3 homeobox 2 (Nkx3.2) was pseudogenised in both platypus and echidna. We speculate that pyloric-like restriction in the echidna may correlate with independent evolution of Grem1 and Bmp4 sequences, and that the convergent loss of gastric acid and stomach size genotypes and phenotypes in teleost and monotreme lineages may be a result of eco-evolutionary dynamics. These findings reflect the effects of gene loss on phenotypic evolution and further elucidate the genetic control of monotreme stomach anatomy and physiology.

evolutionary biology↗