PRM2 and hyperinsulinemic hypoglycemia, familial, 4: The establishment of Prm2−/− mouse strain has unveiled a notable link between Protamine 2 deficiency and male infertility characterized by morphologically impaired and immotile sperm (Schneider et al., 2016), and a follow-up study (Schneider et al., 2020a) suggested a possible molecular mechanism behind described sperm dysfunction.