The hypothalamic arcuate nucleus is the site of expression of several genes known to be important for puberty, including Kiss1 and Tac2.29,30 To assess Mkrn3 mRNA levels in the arcuate nucleus of mice, we performed quantitative real-time PCR (Fig. 3). In both male and female mice, Mkrn3 mRNA levels were highest on postnatal days 10 and 12, began to decline on day 15, and reached a nadir by days 18 to 22, at which time Mkrn3 expression was 10 to 20% of the levels detected at 10 days. The timing of the decline in Mkrn3 expression correlated with the ages at which arcuate Kiss1 and Tac2 expression have been shown to increase, heralding the onset of puberty.24,31 The expression of Mkrn3 remained low through day 45, the oldest age at which the mice were tested (Fig. 3).
