This nonsense mutation was most likely to be responsible for a reduction of AFP mRNA stability, thus resulting in a premature RNA degradation, but this hypothesis could not be verified. order to search for eventual modifications of the amniotic fluid profile, proteins AMG 487 S-enantiomer were separated by electrophoresis and compared with 10 normal amniotic fluids sampled at the same developmental age (18 weeks). In the amniotic fluid of our patient albumin rate MAP3K5 was reduced whereas alpha1 and beta protein fractions were increased, suggesting that AFP deficiency may modify the distribution of protein fractions. This observation emphasizes the complex molecular mechanisms of compensation of serum protein deficiency. Studies on other families with AFP deficiency are necessary to confirm this observation. Keywords:congenital AFP deficiency, Down syndrome screening, protein regulation == Introduction == Alpha feto-protein (AFP) is a major plasma protein produced by the yolk sac and the liver during the fetal period. This fetal protein diffuses in maternal circulation through the placenta and can be detected in the maternal plasma. During the second trimester of pregnancy, serum APF and hCG are commonly used for evaluating the risk of Down syndrome. 1Low and high levels of AFP are indicative of Down syndrome and spina bifida, respectively. After birth, theAFPgene expression dramatically decreases to generally undetectable levels. Molecular mechanisms of protein transition between AFP and albumin during the fetal period are currently not completely understood. AFPgene is located on chromosome 4 and is a member of a multigenic family encoding several plasma proteins, such as albumin or vitamin D-binding protein. To date, rare cases of AFP deficiency during fetal life have been reported: 15 in France,24 in Israel,3,4,52 in the United States.6Congenital deficiency was genetically confirmed in only one case. 5The authors identified the deletion c.882_883delCT at the homozygote state in two unrelated families. Here, we report the case of a family originating from Algeria, in whom a new AMG 487 S-enantiomer nucleic substitution in the exon 5 of theAFPgene was identified resulting in AFP deficiency. == Patients and methods == The mother was 27 years old and was nulligest. Her first pregnancy was obtained by intrauterine insemination, owing to asthenozoospermia. At 12 weeks, fetal ultrasound examination showed a single embryo measuring 60 mm (crown-to-rump length) and 1 mm for nuchal translucency. At 14 weeks and 1 day, second trimester maternal serum screening for AMG 487 S-enantiomer Down syndrome was performed measuring AFP and hCG. hCG rate was 237 641 IU/l (4.74 MoM) and AFP was undetectable (<0.06 MoM), resulting in a very high risk of Down syndrome (>1/10). At 15 weeks, fetal ultrasound examination was normal, but at 18 weeks, nasal bones were not seen. Amniocentesis was performed for both chromosomal analysis and biochemical assays. Cytogenetic investigations showed a normal male karyotype 46,XY, without mosaicism. In amniotic fluid, AFP was also undetectable. Fetal ultrasound examinations were performed at weeks 22 and 32 and proved normal. Birth occurred at 37 weeks after rupture of the amniochorionic membrane. The newborn weighted 3050 g and measured 51 cm. He was transferred in the neonatology unit for mild heart rhythm abnormalities. At 4 days, both mother and neonate were discharged. Development and growth were normal. Alpha feto-protein (measured pure in AMG 487 S-enantiomer duplicate) and hCG (diluted at 1/100) level determinations were both performed by immunochemistry (AdviaCentaur immunoassay system, Bayer Healthcare). Briefly, AFP or hCG were picked by monoclonal antibodies bound to paramagnetic particles and revealed with polyclonal antibodies linked to acridinium ester. Thresholds of detection for the two markers were 1.3 ng/ml (1.08 IU/ml) and 2 IU/l, respectively. Risk of Down syndrome was calculated using T21 Bayer Diagnostics software (Bayer Healthcare). Fetal DNA was extracted from cultured amniocytes using QIAamp DNA mini kit (QiaGen, Courtabuf, France). Primers were designed for amplificating the 14 coding exons of theAFPgene (including the intron-exon junctions), using Primer3 (Primer3 website:http://frodo.wi.mit.edu/cgi-bin/primer3/primer3_www.cgi). Both strands of each exon was sequenced on an ABI Prism 3130 sequencer (AppliedBiosystems, Courtaboeuf, France) and compared with theAFPgene reference AMG 487 S-enantiomer (NC_000004.10) sequence using SeqScape 2.0 software (Applied Biosystems). Total proteins and albumin rates were determined on amniotic fluid using photometry method (pyrogallol red-molybdate method, BioMrieux, Lyon, France) and nephelometry (Dade Behring, Marburg, Germany), respectively. After concentration by Minicon B15 (Millipore, Carrigtwohill, Ireland), amniotic proteins were separated by electrophoresis onto agarose gel (Sebia, Evry, France) and protein fractions were determined with Hydrasis 2 detection system (Sebia). Mean (m) and standard deviation () were calculated from a panel of 10 normal amniotic fluids sampled at 18 weeks (amniocentesis for age; no chromosomal abnormality detected). == Results == The sequence of the 14 coding exons of the AFP gene and their flanking regions was compared with the reference sequence. A homozygote nonsense mutation c.543G>A in.