Characterisation and expression profile of the bovine cathelicidin gene repertoire in mammary tissue

Cormac J Whelehan,Andrew T Lloyd,Cliona O’Farrelly,Kieran G Meade,Aspinas Chapwanya,Anne Barry-Reidy,P David Eckersall,Fernando Narciandi

doi:10.1186/1471-2164-15-128

Abstract

BackgroundCathelicidins comprise a major group of host-defence peptides. Conserved across a wide range of species, they have several functions related to host defence. Only one cathelicidin has been found in humans but several cathelicidin genes occur in the bovine genome. We propose that these molecules may have a protective role against mastitis. The aim of this study was to characterise the cathelicidin gene-cluster in the bovine genome and to identify sites of expression in the bovine mammary gland.ResultsBioinformatic analysis of the bovine genome (BosTau7) revealed seven protein-coding cathelicidin genes, CATHL1-7, including two identical copies of CATHL4, as well as three additional putative cathelicidin genes, all clustered on the long arm of chromosome 22. Six of the seven protein-coding genes were expressed in leukocytes extracted from milk of high somatic cell count (SCC) cows. CATHL5 was expressed across several sites in the mammary gland, but did not increase in response to Staphylococcus aureus infection.ConclusionsHere, we characterise the bovine cathelicidin gene cluster and reconcile inconsistencies in the datasets of previous studies. Constitutive cathelicidin expression in the mammary gland suggests a possible role for these host defence peptides its protection.

Highlights

Cathelicidins comprise a major group of host-defence peptides
B) Alignment of bovine cathelicidin precursor proteins with those from human (Homo sapiens, hCAP-18), mouse (Mus musculus, CAMP), horse (Equus caballus, ecath-2), dog (Canis lupus familiaris, CAMP) and chicken (Gallus gallus, cathl2). (See Additional file 1 for details of the mature peptide encoded by each cathelicidin gene.) Conserved residues are indicated by the asterisk
We examined cathelicidin expression in somatic cells isolated from milk samples from animals with high somatic cell counts (SCC), a metric commonly used to detect intramammary infection

Summary

Introduction

Cathelicidins comprise a major group of host-defence peptides. Conserved across a wide range of species, they have several functions related to host defence. One cathelicidin has been found in humans but several cathelicidin genes occur in the bovine genome. We propose that these molecules may have a protective role against mastitis. Production of host-defence peptides (HDPs), important effector molecules of the innate immune response, is key to effective anti-microbial activity at many sites, in many eukaryotic species. Two and three code for the highly conserved N-terminal-coding region of the precursor protein known as the cathelin domain. Exons 1-3 are highly conserved between species with considerable variation in sequence within the exon 4 sequence within and between species These peptides contain two disulfide bonds between cysteine residues C85-C96 and C107-C124

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