We found that MD mothers expressed a reduced level of FcRn on the yolk sac compared to ND mothers (Fig 4I), whereas FcRn expression on the small intestines was comparable between ND and MD offspring (Fig 4J), suggesting that the observed lower antibody titers in MD offspring (Fig 4D–4E) are likely due to a less effective antibody transfer via the placenta/yolk sac during pregnancy. The gene discussed is FCGRT; the disease is Menkes disease.