Exploring the diversity of AVPR2 in Primates and its evolutionary implications.

The current study focuses on the investigation of AVPR2 (VTR2C) protein-coupled receptor variants specific to different primate taxa. AVPR2 is activated by the neurohormone AVP, which modulates physiological processes, including water homeostasis. Our findings reveal positive selection at three AVPR2 sites at positions 190, 250, and 346. Variation at position 250 is associated with human Congenital Nephrogenic Diabetes Insipidus (cNDI), a condition characterized by excessive water loss. Other 13 functional sites with potential adaptive relevance include positions 185, 202, 204, and 252 associated with cNDI. We identified SH3-binding motifs in AVPR2's ICL3 and N-terminus domains, with some losses observed in clades of Cercopithecidae, Callitrichinae, and Atelidae. SH3-binding motifs are crucial in regulating cellular physiology, indicating that the differences may be adaptive. Co-evolution was found between AVPR2 residues and those in the AVP signal peptide/Neurophysin-2 and AQP2, other molecules in the same signaling cascade. No significant correlation was found between these Primates' taxon-specific variants and the bioclimatic variables of the areas where they live. Distinct co-evolving amino acid sequences in functional sites were found in Platyrrhini and Catarrhini, which may have adaptive implications involving glucocorticoid hormones, suggesting varied selective pressures. Further studies are required to confirm these results.

AVPR1b variation and the emergence of adaptive phenotypes in Platyrrhini primates.

Platyrrhini (New World monkeys, NWm) are a group of primates characterized by behavioral and reproductive traits that are otherwise uncommon among primates, including social monogamy, direct paternal care, and twin births. As a consequence, the study of Platyrrhine primates is an invaluable tool for the discovery of the genetic repertoire underlying these taxon-specific traits. Recently, high conservation of vasopressin (AVP) sequence, in contrast with high variability of oxytocin (OXT), has been described in NWm. AVP and OXT functions are possible due to interaction with their receptors: AVPR1a, AVPR1b, AVPR2, and OXTR; and the variability in this system is associated with the traits mentioned above. Understanding the variability in the receptors is thus fundamental to understand the function and evolution of the system as a whole. Here we describe the variability of AVPR1b coding region in 20 NWm species, which is well-known to influence behavioral traits such as aggression, anxiety, and stress control in placental mammals. Our results indicate that 4% of AVPR1b sites may be under positive selection and a significant number of sites under relaxed selective constraint. Considering the known role of AVPR1b, we suggest that some of the changes described here for the Platyrrhini may be a part of the genetic repertoire connected with the complex network of neuroendocrine mechanisms of AVP-OXT system in the modulation of the HPA axis. Thus, these changes may have promoted the emergence of social behaviors such as direct paternal care in socially monogamous species that are also characterized by small body size and twin births.