Gene Loss

Publication Details

Identifier: JB_RR3V48

Curator: Inês Ferreira Amorim

DOI: 10.1007/s00239-021-10025-1

PMID: 34342686

Title:

Functional or Vestigial? The Genomics of the Pineal Gland in Xenarthra.

Abstract:

Vestigial organs are historical echoes of past phenotypes. Determining whether a specific organ constitutes a functional or vestigial structure can be a challenging task, given that distinct levels of atrophy may arise between and within lineages. The mammalian pineal gland, an endocrine organ involved in melatonin biorhythmicity, represents a classic example, often yielding contradicting anatomical observations. In Xenarthra (sloths, anteaters, and armadillos), a peculiar mammalian order, the presence of a distinct pineal organ was clearly observed in some species (i.e., Linnaeus's two-toed sloth), but undetected in other closely related species (i.e., brown-throated sloth). In the nine-banded armadillo, contradicting evidence supports either functional or vestigial scenarios. Thus, to untangle the physiological status of the pineal gland in Xenarthra, we used a genomic approach to investigate the evolution of the gene hub responsible for melatonin synthesis and signaling. We show that both synthesis and signaling compartments are eroded and were probably lost independently among Xenarthra orders. Additionally, by expanding our analysis to 157 mammal genomes, we offer a comprehensive view showing that species with very distinctive habitats and lifestyles have convergently evolved a similar phenotype: Cetacea, Pholidota, Dermoptera, Sirenia, and Xenarthra. Our findings suggest that the recurrent inactivation of melatonin genes correlates with pineal atrophy and endorses the use of genomic analyses to ascertain the physiological status of suspected vestigial structures.

Last update:

06-04-2025

Associated Glosses (98 results)

GlossID	Species	Symbol	Gene Loss Mechanism	Loss Type	Lineage Specific	Citation
GL_CPENGB	Choloepus didactylus	MTNR1A	LOF (frameshift, premature stop, ss)	Full	Choloepus	10.1007/s00239-021-10025-1
GL_CVJQBJ	Phoca vitulina	MTNR1B	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_D1MVME	Ailuropoda melanoleuca	MTNR1B	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_DB9GKT	Rhinopithecus roxellana	ASMT	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_DC1KJ5	Manis javanica	MTNR1A	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_EKSWRV	Galeopterus variegatus	AANAT	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_EL3AAB	Ursus maritimus	MTNR1B	Exon(s) deletion	Full	Ursus	10.1007/s00239-021-10025-1
GL_EYBQWG	Dugong dugon	AANAT	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1
GL_FM2MOA	Pongo abelii	MTNR1B	LOF (frameshift, premature stop, ss)	Polymorphic	No	10.1007/s00239-021-10025-1
GL_FWK1GN	Balaenoptera musculus	MTNR1B	LOF (frameshift, premature stop, ss)	Full	No	10.1007/s00239-021-10025-1