Gene Loss

Publication Details

Identifier: JB_GXMPRN

Curator: Nádia Silva

Title:

Parallel Independent Losses of G-Type Lysozyme Genes in Hairless Aquatic Mammals.

Abstract:

Lysozyme enzymes provide classic examples of molecular adaptation and parallel evolution, however, nearly all insights to date come from chicken-type (c-type) lysozymes. Goose-type (g-type) lysozymes occur in diverse vertebrates, with multiple independent duplications reported. Most mammals possess two g-type lysozyme genes (Lyg1 and Lyg2), the result of an early duplication, although some lineages are known to have subsequently lost one copy. Here we examine g-type lysozyme evolution across >250 mammals and reveal widespread losses of either Lyg1 or Lyg2 in several divergent taxa across the mammal tree of life. At the same time, we report strong evidence of extensive losses of both gene copies in cetaceans and sirenians, with an additional putative case of parallel loss in the tarsier. To validate these findings, we inspected published short-read data and confirmed the presence of loss of function mutations. Despite these losses, comparisons of selection pressures between intact g- and c-type lysozyme genes showed stronger purifying selection in the former, indicative of conserved function. Although the reasons for the evolutionary loss of g-type lysozymes in fully aquatic mammals are not known, we suggest that this is likely to at least partially relate to their hairlessness. Indeed, although Lyg1 does not show tissue-specific expression, recent studies have linked Lyg2 expression to anagen hair follicle development and hair loss. Such a role for g-type lysozyme would explain why the Lyg2 gene became obsolete when these taxa lost their body hair.

Last update:

01-04-2025

Associated Glosses (98 results)

GlossID	Species	Symbol	Gene Loss Mechanism	Loss Type	Lineage Specific	Citation
GL_HBFLK0	Tursiops truncatus	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_HKZYEQ	Eubalaena japonica	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_HSZHDD	Dugong dugon	LYG1	LOF (frameshift, premature stop, ss)	Full	Sirenia	10.1093/gbe/evab201
GL_IB3TYC	Globicephala melas	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_IP0ZVV	Rhinopithecus bieti	LYG1	Exon(s) deletion	Full	No	10.1093/gbe/evab201
GL_IUP8OS	Physeter catodon	LYG2	LOF (frameshift, premature stop, ss)	Full	No	10.1093/gbe/evab201
GL_J7CNDD	Megaptera novaeangliae	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_JCD0EJ	Neophocaena asiaeorientalis	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_JTA6PY	Delphinapterus leucas	LYG1	LOF (frameshift, premature stop, ss)	Full	Cetacea	10.1093/gbe/evab201
GL_JUC7GY	Tragulus javanicus	LYG1	Exon(s) deletion	Full	No	10.1093/gbe/evab201