Biallelic hypomorphic variants in ALDH1A2 cause a novel lethal human multiple congenital anomaly syndrome encompassing diaphragmatic, pulmonary, and cardiovascular defects

This study shows a causal association between ALDH1A2 variants and a novel, severe multiple congenital anomaly syndrome in humans that is neonatally lethal due to associated pulmonary hypoplasia and respiratory failure. In two families, exome sequencing identified compound heterozygous missense variants in ALDH1A2. ALDH1A2 is involved in the conversion of retinol (vitamin A) into retinoic acid (RA), which is an essential regulator of diaphragm and cardiovascular formation during embryogenesis. Reduced RA causes cardiovascular, diaphragmatic, and associated pulmonary defects in several animal models, matching the phenotype observed in our patients. In silico protein modeling showed probable impairment of ALDH1A2 for three of the four substitutions. In vitro studies show a reduction of RA. Few pathogenic variants in genes encoding components of the retinoic signaling pathway have been described to date, likely due to embryonic lethality. Thus, this study contributes significantly to knowledge of the role of this pathway in human diaphragm and cardiovascular development and disease. Some clinical features in our patients are also observed in Fryns syndrome (MIM# 229850), syndromic microphthalmia 9 (MIM# 601186), and DiGeorge syndrome (MIM# 188400). Patients with similar clinical features who are genetically undiagnosed should be tested for recessive ALDH1A2-deficient malformation syndrome.

Declining prevalence of cystic fibrosis since the introduction of newborn screening

OBJECTIVES

Newborn screening for cystic fibrosis (CF) facilitates early diagnosis and genetic counselling for parents of affected infants. Many parents elect to use prenatal testing for subsequent pregnancies, and this may affect the prevalence of CF. The aim of this study was to assess the evidence for changes in the live-birth prevalence of CF since the introduction of newborn screening for CF.

METHODS

The authors reviewed the records of the Victorian newborn screening programme and the clinical records of the three centres caring for patients with CF in Victoria, Australia, in order to determine the live-birth prevalence of patients with CF; before (1979-1988) and after (1989-2006) the introduction of newborn screening. The authors reviewed the records of the Victorian Clinical Genetics Service to ascertain the number and outcome of prenatal tests for CF (1979-2006). Live births in Victoria were obtained from the state birth register.

FINDINGS

Between 1979 and 1988, the live-birth prevalence of CF was 3.96 (95% CI 3.48 to 4.49) per 10 000 live births. Following the introduction of newborn screening (1989-2006) the live-birth prevalence of CF was 3.28 (95% CI 2.97 to 3.63) per 10 000 live births, representing a reduction of 17% (95% CI 2% to 29%, p=0.025). In the prescreening period, there were 10 prenatal tests, which identified three affected pregnancies, all of which were terminated. In the later period, there were 304 prenatal tests (mean 17/year), of which 76 were affected, and 70 of these pregnancies were terminated.

CONCLUSION

The authors observed a modest reduction in the live-birth prevalence of CF since the introduction of newborn screening. This is principally due to at-risk couples detected by newborn screening electing to use prenatal testing on subsequent pregnancies.

Eutopic and ectopic macromolecular human placental lactogen

Macromolecular forms of human placental lactogen have received little attention because it has been thought that such forms either compose only a small fraction of total immunoactive placental lactogen or are merely laboratory artifacts. We examined serum and placental tissue from women with normal pregnancy (first and third trimesters), serum and tissue from women with eutopic tumors (mole and choriocarcinoma), and serum from men with ectopic placental lactogen production. Samples were chromatographed on dextran gel (Sephadex G-100), and placental lactogen was measured in the fractions by radioimmunoassay. In all specimens examined, immunoactive placental lactogen was found at the void volume of the column (molecular weight greater than 150,000 daltons). This macromolecular placental lactogen comprised less than 4% of total placental lactogen in the third trimester, in mole, and in 16 of 18 first-trimester samples but was significantly higher, up to 19%, in the malignant cases. In two first-trimester placental extracts (but not in their matched sera) macromolecular placental lactogen was the dominant (greater than 45% of the total placental lactogen) immunoactive species. Authentic monomeric placental lactogen was not converted to macromolecular placental lactogen by repeated freezing and thawing. Third-trimester placental macromolecular placental lactogen was unstable; only 13% remained at the void on rechromatography. First-trimester placental macromolecular placental lactogen, on the other hand, was stable to rechromatography. The behavior of immunochemical dilutions of macromolecular placental lactogen from first-trimester placenta was similar to that of monomeric placental lactogen in the same sample. Macromolecular placental lactogen is probably not artifact, and it can comprise a large fraction of the total immunoactive placental lactogen in certain conditions.