Model Systems for Studying Kisspeptin Signalling: Mice and Cells - Kisspeptin Signaling in Reproductive Biology - page 484

Fig. 22.4 Absence of POMC expression in Kiss1 neurons. POMC neurons ( arrowed ) were visual-
ized by immunohistochemistry using an anti-beta-endorphin antibody. Kiss1 neurons were visual-
ized by β-galactosidase activity ( blue dots ). No co-localization of POMC in Kiss1 neurons was
observed in the arcuate nucleus of the hypothalamus of male heterozygous Kiss1 tm1Coll mice. ( a , c )
2 weeks old; ( b , d ) 1 month old. ( a , b ) with 1:5,000 dilution of anti-beta-endorphin antibody
(Peninsula Laboratories Inc.). ( c , d ) No primary antibody. 3V third ventricle. Scale bars = 500 mm
inputs that might modulate their physiological responses to neurotransmitters or neu-
ropeptides. Most of the immortalized cell lines are derived from embryonic neurons
since retroviral delivery of SV40 T-antigen requires proliferating cells and does not
work in post-mitotic adult neurons. This raises the question of how accurately immor-
talized cells model adult neurons. In addition, cell immortalization is associated with
a number of genetic and epigenetic changes, which may alter the gene expression
profi le of the cell compared with its progenitor. For example, the rHypoE-7 and rHy-
poE-8 cell lines co-express Kiss1 and Pomc [ 91 ], but co-expression has not been
found in vivo [ 93 ] and we have failed to detect POMC co-expression in the Kiss1 tmColl
mice (see Fig. 22.4 ). Moreover, RT-PCR analysis of mRNA isolated from adult
Kiss1-GFP neurons has also failed to detect Pomc expression [ 42 ] (Table 22.2 ).
Future Directions
Undoubtedly, transgenic mice will continue to play a signifi cant role in understand-
ing the key molecules that regulate the mammalian reproductive axis. Mouse muta-
genesis programmes, such as those being undertaken by the International Knock-out