Sarcospan, a candidate gene of fat distribution, may affect lipid storage in adipocytes

Genetic and epigenetic variations in the Sarcospan (SSPN) gene are associated with parameters of fat distribution (body mass index, waist-to-hip ratio), glucose homeostasis and adipocyte size in human potentially by affecting adipogenesis. This study aims at clarifying the impact of SSPN on adipogenesis, particularly focusing on its promoter methylation.

Immortalized murine epididymal preadipocytes were transfected with fluorescence-marked plasmids coding for DNMT3a, CRISPR/dCas9-Suntag and vectors carrying guide RNAs complementary to the transcription start site region and differentiated to mature adipocytes. We performed siRNA-mediated Sspn knockdown in epididymal preadipocytes, measured target DNA methylation using pyrosequencing and quantified transcriptional changes of Sspn and adipogenic genes by qPCR. Additionally, we correlated SSPN mRNA values and clinical characteristics from a large human adipose tissue biobank (Leipzig Obesity Biobank).

Epigenetic editing of the Sspn regulatory region in preadipocytes resulted in a significant increase (up to 35 %) in DNA promoter methylation throughout adipocyte differentiation but showed only minor effects on Sspn expression and fat storage. Though siRNA knockdown could also not contribute to understand the role of Sspn in a 2D adipogenesis model, large-scale correlation analyses still indicate the gene to be a key player in fat distribution and glucose homeostasis.

Although the epigenetic downregulation of Sspn showed only marginal effects on adipogenesis, associations of SSPN expression in human adipose tissue with parameters of fat distribution and glucose homeostasis make it a promising candidate for further studies addressing metabolic processes in adipose tissue.