Rab32 and Rab38 genes in chordate pigmentation: an evolutionary perspective

Abstract

BackgroundThe regulation of cellular membrane trafficking in all eukaryotes is a very complex mechanism, mostly regulated by the Rab family proteins. Among all membrane-enclosed organelles, melanosomes are the cellular site for synthesis, storage and transport of melanin granules, making them an excellent model for studies on organelle biogenesis and motility. Specific Rab proteins, as Rab32 and Rab38, have been shown to play a key role in melanosome biogenesis. We analysed the Rab32 and Rab38 genes in the teleost zebrafish and in the cephalochordate amphioxus, gaining insight on their evolutionary history following gene and genome duplications.ResultsWe studied the molecular evolution of Rab supergroup III in deuterostomes by phylogenetic reconstruction, intron and synteny conservation. We discovered a novel amino acid stretch, named FALK, shared by three related classes belonging to Rab supergroup III: Rab7L1, Rab32LO and Rab32/Rab38. Among these, we demonstrated that the Rab32LO class, already present in the last common eukaryotic ancestor, was lost in urochordates and vertebrates. Synteny shows that one zebrafish gene, Rab38a, which is expressed in pigmented cells, retained the linkage with tyrosinase, a protein essential for pigmentation. Moreover, the chromosomal linkage of Rab32 or Rab38 with a member of the glutamate receptor metabotropic (Grm) family has been retained in all analysed gnathostomes, suggesting a conserved microsynteny in the vertebrate ancestor. Expression patterns of Rab32 and Rab38 genes in zebrafish, and Rab32/38 in amphioxus, indicate their involvement in development of pigmented cells and notochord.ConclusionsPhylogenetic, intron conservation and synteny analyses point towards an evolutionary scenario based on a duplication of a single invertebrate Rab32/38 gene giving rise to vertebrate Rab32 and Rab38. The expression patterns of Rab38 paralogues highlight sub-functionalization event. Finally, the discovery of a chromosomal linkage between the Rab32 or Rab38 gene with a Grm opens new perspectives on possible conserved bystander gene regulation across the vertebrate evolution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0596-1) contains supplementary material, which is available to authorized users.

Combined deficiency of RAB32 and RAB38 in the mouse mimics Hermansky-Pudlak syndrome and critically impairs thrombosis

“…41 This would be difficult to reconcile with the fact that RAB32 and RAB38 are paralogs. 14,15 Using 2 different RAB32 antibodies, we found no evidence for this long form of the protein.…”

“…RAB proteins are key mediators of vesicular trafficking. RAB38 and the closely related molecule RAB32 14,15 are expressed in a tissue-specific manner and have been proposed to confer cell-type specificity on LROs, notably on melanosomes. 10,11,16 This is consistent with the phenotype of the fawn-hooded rat, one of the first rodent models of HPS.…”

Transcriptome Reveals Multi Pigmentation Genes Affecting Dorsoventral Pattern in Avian Body

“…MC1R is another key gene for melanin synthesis, and its mutations have been found to have significant association with the extended black trait of ducks (Yu et al, 2013). In addition to the well-known candidate genes mentioned above, MLANA, RAB38, OCA2, TSPAN10, and MSLN were also reported to incorporate into the process of melanin synthesis (Lu et al, 2010;Coppola et al, 2016;Seberg et al, 2017;Béziers et al, 2019). The result showed that the difference on the dorsum and ventral side of LBM ducks might be caused by the mRNA expression changes of multi melanin synthesis related genes.…”

Genome analysis of American minks reveals link of mutations in Ras-related protein-38 gene to Moyle brown coat phenotype

“…The RAB38 gene is highly expressed in melanocytes, and RAB38 protein co-localizes with end-stage melanosomes 12,13 . RAB38 participates in the transport of newly synthesized tyrosinase and Tyrp1, which are key enzymes in melanin production from the trans-Golgi network endosomes to maturing melanosomes 14,15 . Mutations in RAB38 gene were previously described in the dilution of coat colour in chocolate (cht) mice 12 and Ruby rats 13 .…”