Somatic Mosaicism in Bulls Estimated from Genome-Wide CNV Array and <b><i>TSPY</i></b> Gene Copy Numbers

Abstract

Somatic mosaicism has become a focus in human research due to the implications of individual genetic variability in disease. Here, we assessed somatic copy number variations (CNVs) in Holstein bulls in 2 respects. We estimated genome-wide CNVs and assayed CNVs of the TSPY gene, the most variable bovine gene from the Y chromosome. Somatic tissues (blood, lung, heart, muscle, testis, and brain) of 4 bulls were arrayed on the Illumina Bovine SNP50k chip and qPCR tested for TSPY copy numbers. Our results showed extensive copy number divergence in tissues within the same animal as well as significant copy number alterations of TSPY. We detected a mean of 31 CNVs per animal among which 14 were of germline origin, as they were constantly present in all investigated tissues of the animal, while 18 were specific to 1 tissue. Thus, 57% of the total number of detected CNVs was the result of de novo somatic events. Further, TSPY copy number was found to vary significantly among tissues as well as among the same tissue type from different animals in a wide range from 7 to 224% of the calibrator. Our study shows significant autosomal and Y-chromosomal de novo somatic CNV in bulls.

Highly dynamic temporal changes of TSPY gene copy number in aging bulls

“…The observed and above discussed individual variability of rTSPY CN could be explained by the action of these recombination mechanisms during meiosis, as the resulting embryo and developing bull would carry an altered TSPY locus. Furthermore, the role of somatic divisions and DNA break repair events in generating CNVs should also be considered, as emphasized by recent findings of extensive rTSPY CN variability among somatic tissues in bulls [9]. There, differential rates of somatic mosaicism were shown between fast and slowly regenerating tissues, by detecting greater CNVs in blood and testis vs. brain or muscle.…”

“…In order to reflect the temporary changes the normalized values were compared relative to the corresponding T0 of the given animal, thus named as rTSPY CN. DNA specific primers for TSPY and SRY were described earlier [6,9] and listed in S1 Table. The 10ul reaction containing 4.5mM primers, 6ng of genomic DNA and 1X SsoFast EvaGreen Supermix (Bio-Rad) was carried out in a CFX96 Touch™ Real-time PCR Detection System (Bio-Rad) with denaturation at 98 ° C for 2 min, followed by 50 cycles of 98 ° C for 5s, 60 ° C for 5s and 72 ° C for 10s.…”

“…Further, significant differences in TSPY CN were recently found among somatic tissues of individual bulls [9]. Higher CN were detected in tissue types with higher cell division rate (e.g.…”