Homozygous and compound-heterozygous mutations in TGDS cause Catel-Manzke syndrome.

Catel-Manzke syndrome is characterized by Pierre Robin sequence and a unique form of bilateral hyperphalangy causing a clinodactyly of the index finger. We describe the identification of homozygous and compound heterozygous mutations in TGDS in seven unrelated individuals with typical Catel-Manzke syndrome by exome sequencing. Six different TGDS mutations were detected: c.892A>G (p.Asn298Asp), c.270_271del (p.Lys91Asnfs(∗)22), c.298G>T (p.Ala100Ser), c.294T>G (p.Phe98Leu), c.269A>G (p.Glu90Gly), and c.700T>C (p.Tyr234His), all predicted to be disease causing. By using haplotype reconstruction we showed that the mutation c.298G>T is probably a founder mutation. Due to the spectrum of the amino acid changes, we suggest that loss of function in TGDS is the underlying mechanism of Catel-Manzke syndrome. TGDS (dTDP-D-glucose 4,6-dehydrogenase) is a conserved protein belonging to the SDR family and probably plays a role in nucleotide sugar metabolism.

Inactivation of LAR family phosphatase genes Ptprs and Ptprf causes craniofacial malformations resembling Pierre-Robin sequence.

Leukocyte antigen related (LAR) family receptor protein tyrosine phosphatases (RPTPs) regulate the fine balance between tyrosine phosphorylation and dephosphorylation that is crucial for cell signaling during development and tissue homeostasis. Here we show that LAR RPTPs are required for normal development of the mandibular and maxillary regions. Approximately half of the mouse embryos lacking both Ptprs (RPTPσ) and Ptprf (LAR) exhibit micrognathia (small lower jaw), cleft palate and microglossia/glossoptosis (small and deep tongue), a phenotype closely resembling Pierre-Robin sequence in humans. We show that jaw bone and cartilage patterning occurs aberrantly in LAR family phosphatase-deficient embryos and that the mandibular arch harbors a marked decrease in cell proliferation. Analysis of signal transduction in embryonic tissues and mouse embryonic fibroblast cultures identifies an increase in Bmp-Smad signaling and an abrogation of canonical Wnt signaling associated with loss of the LAR family phosphatases. A reactivation of ß-catenin signaling by chemical inhibition of GSK3ß successfully resensitizes LAR family phosphatase-deficient cells to Wnt induction, indicating that RPTPs are necessary for normal Wnt/ß-catenin pathway activation. Together these results identify LAR RPTPs as important regulators of craniofacial morphogenesis and provide insight into the etiology of Pierre-Robin sequence.

IMPAD1 mutations in two Catel-Manzke like patients.

Catel-Manzke syndrome is characterized by hyperphalangism with bilateral deviation of the index fingers and micrognathia with or without cleft palate. Some atypical patients present with additional malformations. No molecular basis is yet available. Most patients have an unremarkable family history but autosomal recessive inheritance has been recently suggested in a consanguineous family with recurrence in sibs. Catel-Manzke syndrome has overlapping features with Desbuquois dysplasia type 1 due to CANT1 (calcium-activated nucleotidase 1) mutations and also with "chondrodysplasia with joint dislocations, gPAPP type" due to IMPAD1 (Inositol Monophosphatase Domain containing 1) mutations recently reported in four patients, all characterized by short stature, joint dislocations, brachydactyly and cleft palate. The aim of our study was to screen CANT1 and IMPAD1 in Catel-Manzke patients. Three patients were diagnosed as classical Catel-Manzke syndrome and two as Catel-Manzke like patients, based on the presence of additional features. We identified two homozygous loss-of-function IMPAD1 mutations in the two Catel-Manzke like patients (p.Arg187X and p.Ser108ArgfsX48). The phenotype was characterized by severe growth retardation with short and abnormal extremities, cleft palate with micrognathia and knee hyperlaxity. Radiographs of hands and feet revealed numerous accessory bones with abnormally shaped phalanges and carpal synostosis. Based on this report, we concluded that IMPAD1 should be screened for patients with Catel-Manzke and additional features.

The molecular mechanism underlying Roberts syndrome involves loss of ESCO2 acetyltransferase activity.

Roberts syndrome/SC phocomelia (RBS) is an autosomal recessive disorder with growth retardation, craniofacial abnormalities and limb reduction. Cellular alterations in RBS include lack of cohesion at the heterochromatic regions around centromeres and the long arm of the Y chromosome, reduced growth capacity, and hypersensitivity to DNA damaging agents. RBS is caused by mutations in ESCO2, which encodes a protein belonging to the highly conserved Eco1/Ctf7 family of acetyltransferases that is involved in regulating sister chromatid cohesion. We identified 10 new mutations expanding the number to 26 known ESCO2 mutations. We observed that these mutations result in complete or partial loss of the acetyltransferase domain except for the only missense mutation that occurs in this domain (c.1615T>G, W539G). To investigate the mechanism underlying RBS, we analyzed ESCO2 mutations for their effect on enzymatic activity and cellular phenotype. We found that ESCO2 W539G results in loss of autoacetyltransferase activity. The cellular phenotype produced by this mutation causes cohesion defects, proliferation capacity reduction and mitomycin C sensitivity equivalent to those produced by frameshift and nonsense mutations associated with decreased levels of mRNA and absence of protein. We found decreased proliferation capacity in RBS cell lines associated with cell death, but not with increased cell cycle duration, which could be a factor in the development of phocomelia and cleft palate in RBS. In summary, we provide the first evidence that loss of acetyltransferase activity contributes to the pathogenesis of RBS, underscoring the essential role of the enzymatic activity of the Eco1p family of proteins.

Caffeine acetylator phenotyping during maturation in infants.

Caffeine acetylator phenotype was studied during maturation in 54 8- to 447-d-old children hospitalized for minor disease (group A) and in five 3- to 630-d-old children with Pierre Robin syndrome (group B). In group A, the children received 2.5 mg/kg caffeine orally once between birth and 15 mo. Group B patients were chronically treated with caffeine (2.3 to 15.8 mg/kg/d) for prevention of apneas, and the acetylator phenotype was serially determined. Phenotyping was performed on a spot urine sample collected 2-6 h after drug administration. Caffeine metabolites [5-acetylamino-6-formylamino-3-methyl uracil (AFMU), 1-methylxanthine, 1-methyluric acid, 1,7-methyluric acid, and 1,7-methylxanthine] were measured using HPLC. Acetylator phenotype was determined on the basis of AFMU/1-methylxanthine (ratio 1) and AFMU/AFMU + 1,7-methyluric acid + 1-methylxanthine + 1,7- methylxanthine + 1,7-methyluric acid (ratio 2) molar ratios. In group A, all children were slow acetylators before 83 d of age (ratio 1 less than 0.4; ratio 2 less than 0.08), whereas older children included slow and fast acetylators. The acetylation molar ratios differed significantly between age groups and increased with age. The cumulative percentage of fast acetylators increased with age but the plateau was not yet reached at 15 mo. In three children, the phenotyping was repeated after 15 mo: the second determination was consistent with the first one. In group B, all children appeared as slow acetylators on the first phenotyping. Four of them appeared subsequently as fast acetylators; one remained a slow acetylator until 11 mo.(ABSTRACT TRUNCATED AT 250 WORDS)