Gene Loss

Publication Details

Identifier: JB_HVKHQU

Curator: M. Lopes-Marques

Title:

Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales.

Abstract:

Whales in the suborder Mysticeti are filter feeders that use baleen to sift zooplankton and small fish from ocean waters. Adult mysticetes lack teeth, although tooth buds are present in foetal stages. Cladistic analyses suggest that functional teeth were lost in the common ancestor of crown-group Mysticeti. DNA sequences for the tooth-specific genes, ameloblastin (AMBN), enamelin (ENAM) and amelogenin (AMEL), have frameshift mutations and/or stop codons in this taxon, but none of these molecular cavities are shared by all extant mysticetes. Here, we provide the first evidence for pseudogenization of a tooth gene, enamelysin (MMP20), in the common ancestor of living baleen whales. Specifically, pseudogenization resulted from the insertion of a CHR-2 SINE retroposon in exon 2 of MMP20. Genomic and palaeontological data now provide congruent support for the loss of enamel-capped teeth on the common ancestral branch of crown-group mysticetes. The new data for MMP20 also document a polymorphic stop codon in exon 2 of the pygmy sperm whale (Kogia breviceps), which has enamel-less teeth. These results, in conjunction with the evidence for pseudogenization of MMP20 in Hoffmann's two-toed sloth (Choloepus hoffmanni), another enamel-less species, support the hypothesis that the only unique, non-overlapping function of the MMP20 gene is in enamel formation.

Last update:

02-07-2024

Associated Glosses (9 results)

GlossID	Species	Symbol	Gene Loss Mechanism	Loss Type	Citation
GL_3LMHQ7	Eubalaena australis	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_7IVQV2	Balaenoptera acutorostrata	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_CHWNWA	Megaptera novaeangliae	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_EKUIFA	Eschrichtius robustus	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_ENZCWX	Balaena mysticetus	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_HX716Q	Caperea marginata	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_JZEKYN	Balaenoptera physalus	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_SLCFEZ	Balaenoptera musculus	MMP20	Other	Full	10.1098/rspb.2010.1280
GL_YNFIOL	Kogia breviceps	MMP20	Other	Polymorphic	10.1098/rspb.2010.1280