Transcriptome analysis of fetal Klinefelter testis tissue samples compared to controls. Homo sapiens

In humans, the most common sex chromosomal disorder is Klinefelter syndrome (KS), caused by the presence of one or more extra X-chromosomes. The KS patients display a diverse adult phenotype with increased height, gynaecomastia, and hypergonadotropic hypogonadism as the most common symptoms. Men with KS are almost always infertile due to testicular degeneration, which accelerates during puberty. Very few studies investigated when the germ cell loss begins and whether it is caused by dysgenetic fetal development of the testes. We investigated a series of fetal KS testis tissue samples and found a marked reduction in MAGE-A4-positive pre-spermatogonia in the developing KS gonads compared to controls, indicating a failure of the gonocytes to differentiate into pre-spermatogonia. Transcriptome analysis by RNA sequencing of formalin-fixed and paraffin embedded gonads originating from 4 fetal KS samples and 5 age- and cellularity-matched controls revealed 211 differentially expressed transcripts in the fetal KS testis. We found a significant enrichment of upregulated X-chromosomal transcripts and validated the expression of the pseudoautosomal region 1 (PAR1) gene, AKAP17A. Moreover, we found enrichment of long non-coding RNAs in the KS testes (e.g. LINC01569 and RP11-485F13.1). In conclusion, our data indicates that the testicular phenotype observed among adult men with KS is initiated already in fetal life by failure of the gonocyte differentiation into pre-spermatogonia, which could be due to aberrant expression of long non-coding RNAs. Overall design: Includes a total of 9 samples. 4 fetal Klinefelter and 5 age-matched controls testis samples