Human genetics and epidemiological studies have indicated that multiple genes and environmental factors are involved in onset of neurodevelopmental diseases such as autism. Here we would like to propose our mouse model that a neurodevelopmental gene Pax6 and advanced paternal age are cross-interacted risk factors for vocal communication deficits assayed by maternal separation-induced ultrasonic vocalization (USV). To obtain F1 offspring, young C57BL6/J (3-month-old) female mice were mated with male wild type (WT) or Sey/+ mice at three different ages, i.e., young, middle-aged (6-8-month-old) and advanced aged (>12-month old). F2 offspring were obtained from crossing young C57BL6/J female mice with young F1 WT offspring derived from young or advanced aged F0 WT father. USV of both F1 and F2 offspring was measured at postnatal day 6. The number of USV in WT offspring derived from advanced-aged WT was dramatically decreased by 32.7% and 33.1% compared to that in WT offspring derived from young and middle-aged WT, respectively. In contrast, the number of USV was not different between the groups in F2 offspring, implicating that the USV phenotype would be canceled in the next generation. Interestingly, the number of USV in Sey/+ offspring derived from middle-aged Sey/+ was significantly decreased by 58.8% compared to that in WT offspring. In contrast, the number of USV was not statistically altered between WT and Sey/+ offspring derived from young Sey/+, indicating that Pax6 haploinsufficiency precociously affects USV phenotypes. To explore molecular mechanisms, histone methylation moieties were compared between young versus advanced aged or middle aged WT versus Sey/+ spermatocytes, in which Pax6 is predominantly expressed. We found significant changes in global methylation in advanced aged and middle-aged Sey/+ spermatocytes. Our results suggest an intriguing possibility that epigenetical changes in spermatogenesis may cause behavioral abnormalities such as maternal separation-induced USV in the offspring. We are testing whether these altered histone methylation remains in sperm and in the developing brain.