Across deserts and Andes: a genetic exploration of GlyCam-1 in domestic camelids

Lactophorin is a major whey protein in camelid milk that prevents fat globule aggregation and inhibits spontaneous lipolysis. It has also been proposed to play immunological functions, including the prevention of mastitis in lactating animals and the suppression of pathogen replication in the respiratory and gastrointestinal tracts of suckling offspring. In this study, we explore the genetic variation of the glycosylation-dependent cell adhesion molecule-1 (GlyCam-1) gene in camelids, which encodes lactophorin, and examine the functional implications of the identified polymorphisms.

The regulatory regions and the complete gene were sequenced and analysed in the Old World Camelids (OWC, dromedary and bactrian) and New World Camelids (NWC, llama and alpaca) using an integrated approach of molecular techniques and bioinformatics. The GlyCam-1 gene spans 2,567 bp in OWC and 2,504 bp in NWC and consists of 4 exons and 3 introns, highlighting its conserved structure. Sequencing results revealed inter- and intraspecies genetic variation, with 18 polymorphic sites in dromedaries, 7 in bactrian camels, 32 in alpacas, and 40 in llamas. Significant exonic polymorphisms were observed in NWC, potentially affecting gene expression and protein structure. Notably, the p.Glu46Lys and p.Ser134Pro variants in NWC were predicted to have a deleterious effect on protein function. Regulatory region analysis identified SNPs predicted to alter transcription factor binding sites (TFBS). In dromedaries, the g.563C > T substitution was predicted to affect the NF-κB binding, whereas in NWC, g.163A > G was predicted to modify a MZF1 binding site. The first SNP was associated with increased gene expression, and the latter was linked to significantly lower gene expression as a result of dual-luciferase reporter gene assay. Five haplotypes were observed in both NWC, with AGG and AGGG being the most prevalent in alpacas (0.707) and llamas (0.803), respectively; whereas a deviation from Hardy-Weinberg equilibrium was found for the SNP g.163A > G in alpacas.

This study underscores the evolutionary conservation of GlyCam-1, highlights the importance of the found genetic variants and their potential use as candidate markers for future association studies with immune regulation and dairy traits.