ABSTRACT
Thermal adaptation to environmental temperature is a driving force in animal evolution. This chapter presents thermal adaptation in ectotherms and endotherms from the perspective of developmental biology. In ectotherms, there are known examples of temperature influencing morphological characteristics, such as seasonal color change, melanization, and sex determination. Furthermore, the timing of embryonic development also varies with environmental temperature. This review will introduce the cellular and molecular mechanisms underlying temperature-dependent embryogenesis. The evolution of thermal adaptation in endotherms is also important for survival in cold climates. Recent genome-wide studies have revealed adaptive mutations in the genomes of extant humans as well as extinct species such as woolly mammoths and Neanderthals. These studies have shown that single-nucleotide polymorphisms in physiologically related genes (e.g., CPT1A, LRP5, THATA, PRKG1, and FADS1-3) allow humans to live in cold climates. At the end of this chapter, we present the remaining questions in terms of genetic assimilation, heat shock protein Hsp90, and embryonic development.
Subject(s)
Embryonic Development , Animals , Humans , Embryonic Development/genetics , HSP90 Heat-Shock Proteins/genetics , HSP90 Heat-Shock Proteins/metabolism , Biological Evolution , Delta-5 Fatty Acid Desaturase , Fatty Acid Desaturases/genetics , Fatty Acid Desaturases/metabolism , Evolution, Molecular , Adaptation, Physiological/genetics , Polymorphism, Single Nucleotide , Thermotolerance/genetics , Acclimatization/geneticsABSTRACT
Changes in genomic structures underlie phenotypic diversification in organisms. Amino acid-changing mutations affect pleiotropic functions of proteins, although little is known about how mutated proteins are adapted in existing developmental programs. Here we investigate the biological effects of a variant of the GLI3 transcription factor (GLI3R1537C) carried in Neanderthals and Denisovans, which are extinct hominins close to modern humans. R1537C does not compromise protein stability or GLI3 activator-dependent transcriptional activities. In contrast, R1537C affects the regulation of downstream target genes associated with developmental processes. Furthermore, genome-edited mice carrying the Neanderthal/Denisovan GLI3 mutation exhibited various alterations in skeletal morphology. Our data suggest that an extinct hominin-type GLI3 contributes to species-specific anatomical variations, which were tolerated by relaxed constraint in developmental programs during human evolution.