Differential gene expression in skin RNA of horses affected with degenerative suspensory ligament desmitis

Abstract

Background Equine degenerative suspensory ligament desmitis (DSLD) is a systemic connective tissue disorder first identified in Peruvian Paso horses but afflicting other horse breeds as well. Inappropriate accumulation of proteoglycans in connective tissues, most prominently in tendons and ligaments, leads to progressive and debilitating lameness and pain. It is largely unknown what drives the overproduction of proteoglycans, but our previous studies suggest involvement of bone morphogenetic protein 2 (BMP2), a member of the transforming growth factor-β (TGFβ) family, impacting synthesis of proteoglycans. To identify potential players in pathogenesis of DSLD a new approach utilizing next generation sequencing was undertaken. Methods Next generation sequencing was performed using RNA extracted from skin biopsies of six control Peruvian Pasos and six horses with DSLD (4 Peruvian Pasos and 2 warmbloods). The CuffDiff result sets were validated with algorithms used to run them. This was based on the determined false discovery rates derived from the P values adjusted for multiple testing for any given result. Results Bioinformatics analysis of transcriptomes revealed differential expression of over 1500 genes, including increased expression of genes for several growth factors (most prominently BMP2, FGF5, CTGF, many members of the EGF family), and mediators of signaling (Fos, Myc, MAPK system), and keratins. Two genes encoding for enzymes involved in synthesis of hyaluronan were also overexpressed. Gene expression was decreased for protein cores of many proteoglycans, several growth factors, most collagens, and many peptides with immune function. Conclusions The overexpression of BMP2 correlates well with our previous data. However, the decrease in expression of numerous proteoglycans was unexpected. A mutation in a gene of a less characterized proteoglycan and/or glycosyltransferase with subsequent increased production of hyaluronan and/or a proteoglycan(s) undetected in our study could account for the systemic proteoglycan deposition. Decreased collagen gene expression indicates abnormal connective tissue metabolism. The increased expression of keratin genes and FGF5 supports reports of skin abnormalities in DSLD. Underexpression of immune function genes corresponds with lack of inflammation in DSLD tissues. Finally, though the proteoglycan and/or glycosaminoglycan abundant in DSLD has not been identified, we validated our previous data, including overexpression of BMP2, and systemic nature of DSLD due to disturbed metabolism of the extracellular matrix.

Selection signature analyses and genome-wide association reveal genomic hotspot regions that reflect differences between breeds of horse with contrasting risk of degenerative suspensory ligament desmitis

“…Collagen VI is an extracellular matrix protein with critical roles in maintaining muscle and skin integrity ( Lamande and Bateman 2018 ). The role of COL6A5 mutations in the development of myopathy and fibrosis is not understood ( Sabatelli et al 2011 ), but the expression of COL6A5 is decreased in the skin of DSLD-affected horses ( Haythorn et al 2020 ).…”

“…During past decades, investigation of the molecular pathology of DSLD, disturbances to signaling pathways, genome-wide analysis with low-density markers, and case–control gene expression analysis have been performed ( Young et al 2018 ; Mero and Pool 2002 ; Haythorn et al 2020 ). A low-resolution genome-wide association study (GWAS) in the PH identified candidate loci on Equus caballus autosomes (ECAs) 6, 7, 11, 14, and 26 that did not meet genome-wide significance ( Strong 2005 ; Metzger and Distl 2020 ).…”

Identification of Potential Abnormal Methylation-Modified Genes in Coronary Artery Ectasia

“…ADAM12 is also implicated in processes of excessive growth, such as cardiac hypertrophy [ 38 ]. IGSF10, a pro-inflammatory cytokine, is down-regulated in calcific aortic valve disease [ 39 , 40 ]. SGCD is associated with aortic pathology [ 41 ].…”

A one-health lens offers new perspectives on the importance of endocrine disorders in the equine athlete

“…Insulin dysregulation associated with EMS and PPID 27,35,112,113,[149][150][151][152][153] Suspensory ligament desmitis/degeneration PPID 119,120,154,155 Muscle atrophy and possible secondary back pain PPID 24,26,75,126 Obesity and lameness, exercise intolerance Obesity, EMS due to suppression from high circulating levels of glucocorticoids, the clinical significance of which is unknown. 39 In humans, hypothyroidism is more clinically significant but only has a weak link to MetS in men.…”