Evidence for a functional role of Start, a long noncoding RNA, in mouse spermatocytes

A mouse testis-specific long noncoding RNA (IncRNA), Start, is localized in the cytosol of Leydig cells and in the nucleus of pachytene spermatocytes. We previously showed that Start regulates steroidogenesis through controlling the expression of Star and Hsd3b1 genes in Leydig cells, but its function in germ cells was not known. Here we verified that a spermatocyte-specific protease gene, Prss43/Tessp-3, was down regulated in Start-knock-out testes. To investigate the transcriptional regulatory activity of Start in spermatocytes, we first performed a series of reporter gene assays using a thymidine kinase promoter in spermatocyte-derived GC-2spd(ts) cells. A 5.4-kb genome sequence encompassing Start exhibited enhancer activity for this promoter, and the activity was decreased by knockdown of Start. Deletion of the Start promoter and replacement of the Start sequence abolished the enhancer activity and, consistently, the activity was detected in further experiments only when Start was actively transcribed. We then examined whether the Prss43/Tessp-3 gene could be a target of Start. A reporter gene assay demonstrated that the 5.4-kb sequence exhibited enhancer activity for a Prss43/Tessp-3 promoter in GC-2spd(ts) cells and that the activity was significantly decreased by knockdown of Start. These results suggest that Start functions in transcriptional activation of the Prss43/Tessp-3 gene in spermatocytes. Given that Start is presumed to regulate steroidogenic genes at the posttranscriptional level in Ley-dig cells, the function in spermatocytes is a novel role of Start. These findings provide an insight into multifunctionality of IncRNAs in the testis.

Automated summary

This study revealed a novel role of a long noncoding RNA named Start in germ cells. Start was found to regulate the transcriptional activation of the Prss43/Tessp-3 gene in spermatocytes, providing new insights into the multifunctionality of IncRNAs in the testis.