The Development of Kisspeptin Circuits in the Mammalian Brain - Kisspeptin Signaling in Reproductive Biology - page 219

Fig. 11.1 Development of the Kiss1 sex difference in the anteroventral periventricular nucleus and
neighboring periventricular nucleus (AVPV/PeN) of mice. Mean number of Kiss1 neurons in the
AVPV/PeN of female and male mice over the course of early postnatal development. Kiss1 cells
were fi rst detected in each sex on PND 10. The number of Kiss1 neurons was signifi cantly higher
in females than males on PND 12 and later. *Signifi cantly different from males of same age.
Modifi ed from Semaan SJ, Murray EK, Poling MC, Dhamija S, Forger NG, Kauffman AS 2010
BAX-dependent and BAX-independent regulation of Kiss1 neuron development in mice.
Endocrinology 151:5807-5817
Another developmental study of kisspeptin protein expression in female mice found
no kisspeptin-immunoreactive (ir) cells in the AVPV/PeN at PND 10 and only a
small number of kisspeptin cells at PND 15, which was the next chronological age
examined [ 62 ]. Whether the absence of detectable kisspeptin-ir cells at PND 10
refl ects differences in the sensitivities of the techniques used (IHC vs. ISH) or a
developmental difference at the level of either post-transcriptional processing or
translation is currently unknown.
Looking beyond the fi rst 2 weeks of life, kisspeptin-ir cell number was found to
steadily increase in the mouse AVPV/PeN from PND 15 to adulthood (assessed
every 5 days of age) [ 62 ]. Extending this protein data, our lab recently performed a
detailed, day-by-day analysis of Kiss1 mRNA expression in prepubertal and puber-
tal female mice and found that Kiss1 cell number in the AVPV/PeN steadily and
continually increases from PND 15 through PND 28, at which point it resembles
adulthood levels [ 63 ]. In rats, like mice, AVPV/PeN kisspeptin expression is not
detectable on PND 4 or PND 8, but is noticeably present by the next age examined,
PND 22 [ 64 ]. Developmental changes in Kiss1 mRNA expression have also been
documented in the POA of ewes [ 65 ] at 25, 30, and 35 weeks of age, and an increase
in POA Kiss1 cell number was observed at 30 weeks, corresponding to the time of
puberty, with no further increase detectable at 35 weeks [ 65 ]. In non-human pri-
mates, KISS1 expression also increases in the hypothalamus during puberty, but this
was attributed to kisspeptin neurons in the medial basal hypothalamic region
(i.e., the ARC) rather than the POA population [ 25 ].