SIK2 and obesity due to melanocortin 4 receptor deficiency: Conversely, one of the members of this group, calreticulin (Calr), decreased in SIK2-deficient POMCs in response to early ER stress induction, and this effect was reversed upon SIK2 overexpression, indicating differential regulation of counteracting factors within the same group (Table 2, see the obesity and feeding behavior group, red colored).