PHOSPHO1 and Stillbirth: Of 272 pups born to Phospho1+/− × Akp2+/− and [Phospho1−/−; Akp2+/−] × [Phospho1−/−; Akp2+/−] matings (Supplemental Table S3), only one double-knockout [Phospho1−/−; Akp2−/−] pup was born, and that was a stillbirth.