First, scRNAseq can be used to identify unusual gene expression patterns or differences in testicular tissue cell composition that are associated with known infertility pathologies such as chromosomal (Klinefelter syndrome; chromosome translocations, inversions, and deletions) or genetic defects (microdeletions in the Y chromosome azoospermia factor region or mutations in the androgen receptor gene, for example) [110,111,112]. The gene discussed is AR; the disease is Klinefelter syndrome.