In our previous study of Sfmbt2 miRNA KO mice, we identified the physiologically important target genes based on their altered expression levels in KO placentas at E8.5 and E11.5 (ref. 32), which included at least four genes that play roles in tumor growth repression or apoptosis (Gkn2, Rgs4, Fndc1, and Fst); therefore, they are likely to regulate the size of the placenta. The gene discussed is GKN2; the disease is neoplasm.