Precocious puberty is puberty occurring at an unusually early age. According to the recent study, a family with precocious puberty is associated with a mutation in the makorin 3(mkrn3) gene.
To determine whether a change in mkrn3 causes similar effects on Drosophila as it does in mammals and to test in vivo and find the mechanism, we chose mkrn1 in drosophila because it is a orthologue of mkrn3.
We made mkrn1 deletion mutant flies by imprecise excision of p-element. To determine the effect of this mutant line on growth and maturation. We checked various aspect of fly. mkrn1exS flies has longer pupation time and pupa length than control flies. Also, we found that mkrn1exS is much more heavier and consumed food than male and control female fly.
Altogether, these results reveal that mkrn1exS affects drosophila growth and maturation.
When we crossed the mutant fly we were able to find that female homozygous mutant drosophila lose their fertility. In the case of ovaries from control flies, vitellogenesis occurs, resulting in the formation of yolk and eggs. In the case of ovaries from mkrn1exS, however, vitellogenesis does not occur, resulting in infertility.
To find out why vitellogenesis does not occur, we checked the InR/TOR signaling pathway. We have confirmed that the mkrn1exS has high activity of InR/TOR signaling pathway. However, abnormal InR/TOR signaling pathway does not seem to be the reason why vitellogenesis does not occur because it is still working.
Also, we checked the Notch signaling pathway. As a result, it was found that mkrn1exS has an abnormal Notch signaling pathway. In addition,.we found that the number of follicle cells expressing cyclin B is higher in mkrn1exS. From these results, we thought that vitellogenesis does not occur because of the abnormality of Notch signaling pathway, which is essential for controlling the cell cycle of the follicle cell. This result is supported by the fact that the cell cycle regulator, Cyclin B, is abnormal. However, it is not yet clear whether this is the direct cause of infertility.
Taken together these results, mkrn1 is required for drosophila oogenesis. However, exact mechanism is unknown yet.
