Dr. Markus Hammel (PhD) Molecular neonatology (K0.21/K0.22) - KUBUS Research Center - Dr. von Hauner Children´s Hospital LMU - University of Munich - Lindwurmstrasse 2a 80337 Munich Phone: ++49-89-5160-7794 Fax: ++49-89-5160-7792
Abstract: BACKGROUND: Congenital Central Hypoventilation Syndrome (CCHS, Ondine's curse) is a rare syndrome of dysfunction of the autonomic nervous system characterized by a decreased response to hypercarbia requiring mechanical ventilation in most cases. CCHS is an autosomal-dominant disease associated with tumors of neural crest origin, segmental aganglionosis of the colon, and diffuse autonomic dysregulation symptoms. Most cases of CCHS are caused by de novo heterozygous in-frame expansions within in the PHOX2b gene. PATIENTS AND MAIN RESULTS: Here we report two families in which a PHOX2b defect was inherited from an asymptomatic parent. In family 1 an asymptomatic mother carried a mild mutation (15 bp expansion within the polyalanine repeat) also found in her daughter who was symptomatic immediately after birth but did not require mechanical ventilation. In family 2, two newborn infants with respiratory failure due to insufficient respiratory drive requiring mechanical ventilation were born to asymptomatic parents. A 39 pb expansion within the PHOX2b polyalanine repeat was found in one patient in whom DNA was available, but not in blood leukocytes from any parent. Microsatellite analyses confirmed the identity of the parents, such that a germline mosaicism has to be deduced. CONCLUSIONS: Carriers of mild PHOX2b mutations causing disease in their offspring may be asymptomatic; Modifier genes determining the clinical course may exist. Germline mosaicism may lead to CCHS in children from unaffected parents. Genetic counseling should include these variations.
Abstract: Mutations in the human ABCA3 gene, encoding an ABC-transporter, are associated with respiratory failure in newborns and pediatric interstitial lung disease. In order to study disease mechanisms, a transgenic mouse model with a disrupted Abca3 gene was generated by targeting embryonic stem cells. While heterozygous animals developed normally and were fertile, individuals homozygous for the altered allele (Abca3-/-) died within one hour after birth from respiratory failure, ABCA3 protein being undetectable. Abca3-/- newborns showed atelectasis of the lung in comparison to a normal gas content in unaffected or heterozygous littermates. Electron microscopy demonstrated the absence of normal lamellar bodies in type II pneumocytes. Instead, condensed structures with apparent absence of lipid content were found. We conclude that ABCA3 is required for the formation of lamellar bodies and lung surfactant function. The phenotype of respiratory failure immediately after birth corresponds to the clinical course of severe ABCA3 mutations in human newborns.
