The cathelicidin Gene Cluster in Goats (Capra hircus): Organization and Diversity

Abstract

The innate immune system is the first line of defence against pathogens. Among these, host defence peptides play a crucial role as they have direct antimicrobial activity and modulate the immune response. Cathelicidins are a well-known HDP found in most vertebrates, including goats. These peptides contribute to the immune system by targeting a broad spectrum of microorganisms being involved in immune regulation. Cathelicidins are structurally diverse and are classified according to the secondary structure of their mature peptides, including α-helices, β-hairpin structures, and elongated forms rich in proline-arginine or tryptophan. Their genes are typically organised in genomic clusters, as seen in ruminants such as sheep and cows. The identification of several cathelicidin genes and their organisation is necessary to understand the organisation and diversity of these antimicrobial peptides in the goat genome. This information provides valuable insights into their role in immune defence and disease resistance. The aim of this study was to identify and characterise the goat cathelicidin cluster using bioinformatics tools and analysis of the reference goat genome. Our results show that all cathelicidin genes in the goat genome are grouped in a cluster on chromosome 22 spanning approximately 75 Kb. It was identified a total of seven cathelicidin genes and one potential pseudogene. The average gene size was 1719 bp and ranged from 1309 bp (CATH1) to 1956 bp (CATH3). The first gene of the cluster, MAP34B, encodes a mature peptide containing a CAP-18 domain, a characteristic LPS-binding domain in mammals. Three cathelicidins exhibited a proline-arginine-rich structure, while the other four adopted an α-helix conformation.