Alternative splicing of DENND1A, a PCOS candidate gene, generates variant 2

Area of Science:

• Endocrinology
• Genetics
• Molecular Biology

Background:

• Polycystic ovary syndrome (PCOS) is a common endocrine disorder linked to hyperandrogenism and metabolic dysfunction.
• The DENND1A gene, implicated in PCOS, encodes two variants: V1 and V2.
• The V2 variant is overexpressed in androgen-producing theca cells of PCOS patients, correlating with increased androgen synthesis.

Purpose of the Study:

• To investigate the origin and regulation of the DENND1A V2 isoform in adrenal cells.
• To explore the role of genetic variation in intron 20 of DENND1A in PCOS pathogenesis.
• To determine if altered V2 expression in adrenal cells contributes to PCOS phenotypes.

Main Methods:

• Analysis of DENND1A V1 and V2 mRNA and protein expression in human adrenal NCI-H295A cells.
• Investigating V2 isoform generation via exonization of intronic sequences.
• Assessing the impact of V2 overexpression on CYP17A1 and CYP11A1 mRNA levels in adrenal cells.
• Genotyping and functional analysis of genetic variants in intron 20 of DENND1A.

Main Results:

• Human adrenal cells express both DENND1A V1 and V2 variants.
• The V2 isoform is generated through the exonization of intron 20 sequences, creating a unique exon 20A.
• Forced V2 expression in adrenal cells increased CYP17A1 and CYP11A1 mRNA abundance, mimicking PCOS theca cell behavior.
• Genetic variations in intron 20 showed no clear association with PCOS and did not consistently promote V2 transcript splicing.

Conclusions:

• The DENND1A V2 isoform is expressed in human adrenal cells and can influence androgen synthesis genes.
• Increased V2 expression in PCOS theca cells is unlikely due to genomic sequence variation in the studied intronic region.
• Further research is needed to elucidate the precise mechanisms regulating V2 expression in PCOS.