Before establishing the mating couples, mice were kept in samesex groups of 2 to 6 littermates. The animals were kept in opaque M3 type cages with dimensions of 48(15(13(cm from North Kent Plastics, UK equipped with bedding ('Eco-bedding', B&K Universal Ltd, UK) and nesting material ('Nestlet', Datesand Ltd, UK). Cages were changed once per week and in case of the nursing females the nesting material was transferred to the new cage. The environment was kept at 21+/(2(C and 55+/(15% relative air humidity with a 12(hour light 12(hour dark cycle (lights off 8:00 pm) Food (BeeKay Transgenic Rodent Diet BK021E, B&K Universal Ltd, UK) and tap water were available ad libitum, water bottles being routinely changed twice per week.