Dear All,

I am interested to identify the most evolutionarily distant orthologues of human GABA-A subunit genes (e.g., GBRA1_HUMAN, GBRA2_HUMAN etc). The human GABA-A receptor is a pentameric GABA-gated chloride channel. A gene with identical domain composition and functional annotation exists in C. elegans (G5EBQ0_CAEEL, a GABA-gated chloride channel). However, this gene is not annotated as an orthologue to the human GABA-A receptor subunits in any database I searched, including Ensembl or OMA. In OMA (CAEEL08801), it is neither detected as a pairwise orthologue nor it maps to the same HOG with the human GABA-A subunits.

I am wondering what would be sufficient evidence to argue that this is an example of convergent evolution, i.e. C. elegans and homo sapiens independently evolved GABA-gated chloride channels from some early precursor? Is the separation at the HOG level in OMA a good indication that pairwise orthology is not detected purely due to large evolutionary distance?

Many thanks for your help with this.

With best wishes,

Andrija