A further study of MTHFR deficiency in early germ cell development found different reproductive phenotypes between 2 strains, BALB/c mice and C57BL/6 mice: BALB/c mice showed an early postnatal loss of germ cell number and proliferation that resulted in infertility with perturbed DNA methylation patterns of imprinted genes in sperms, whereas the C57BL/6 mice exhibited decreased sperm numbers and altered testicular histology but showed normal fertility and unaffected imprinting [Chan et al., 2010]. The gene discussed is MTHFR; the disease is Infertility.