Frank Majewski

Mutation Analysis of Core Binding Factor A1 in Patients with Cleidocranial Dysplasia

Cleidocranial dysplasia (CCD) is a dominantly inherited disorder characterized by patent fontanelles, wide cranial sutures, hypoplasia of clavicles, short stature, supernumerary teeth, and other skeletal anomalies. We recently demonstrated that mutations in the transcription factor CBFA1, on chromosome 6p21, are associated with CCD. We have now analyzed the CBFA1 gene in 42 unrelated patients with CCD. In 18 patients, mutations were detected in the coding region of the CBFA1 gene, including 8 frameshift, 2 nonsense, and 9 missense mutations, as well as 2 novel polymorphisms. A cluster of missense mutations at arginine 225 (R225) identifies this residue as crucial for CBFA1 function. In vitro green fluorescent protein fusion studies show that R225 mutations interfere with nuclear accumulation of CBFA1 protein. There is no phenotypic difference between patients with deletions or frameshifts and those with other intragenic mutations, suggesting that CCD is generally caused by haploinsufficiency. However, we were able to extend the CCD phenotypic spectrum. A missense mutation identified in one family with supernumerary teeth and a radiologically normal skeleton indicates that mutations in CBFA1 can be associated exclusively with a dental phenotype. In addition, one patient with severe CCD and a frameshift mutation in codon 402 had osteoporosis leading to recurrent bone fractures and scoliosis, providing first evidence that CBFA1 may help maintain adult bone, in addition to its function in bone development.

Genotypic and Phenotypic Spectrum in Tricho-Rhino-Phalangeal Syndrome Types I and III

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Three subtypes have been described: TRPS I, caused by mutations in the TRPS1 gene on chromosome 8; TRPS II, a microdeletion syndrome affecting the TRPS1 and EXT1 genes; and TRPS III, a form with severe brachydactyly, due to short metacarpals, and severe short stature, but without exostoses. To investigate whether TRPS III is caused by TRPS1 mutations and to establish a genotype-phenotype correlation in TRPS, we performed extensive mutation analysis and evaluated the height and degree of brachydactyly in patients with TRPS I or TRPS III. We found 35 different mutations in 44 of 51 unrelated patients. The detection rate (86%) indicates that TRPS1 is the major locus for TRPS I and TRPS III. We did not find any mutation in the parents of sporadic patients or in apparently healthy relatives of familial patients, indicating complete penetrance of TRPS1 mutations. Evaluation of skeletal abnormalities of patients with TRPS1 mutations revealed a wide clinical spectrum. The phenotype was variable in unrelated, age- and sex-matched patients with identical mutations, as well as in families. Four of the five missense mutations alter the GATA DNA-binding zinc finger, and six of the seven unrelated patients with these mutations may be classified as having TRPS III. Our data indicate that TRPS III is at the severe end of the TRPS spectrum and that it is most often caused by a specific class of mutations in the TRPS1 gene.

Spectrum of mutations in PTPN11 and genotype-phenotype correlation in 96 patients with Noonan syndrome and five patients with cardio-facio-cutanesous syndrome

Noonan syndrome (NS) is a relatively common, but genetically heterogeneous autosomal dominant malformation syndrome. Characteristic features are proportionate short stature, dysmorphic face, and congenital heart defects. Only recently, a gene involved in NS could be identified. It encodes the non-receptor protein tyrosine phosphatase SHP-2, which is an important molecule in several intracellular signal transduction pathways that control diverse developmental processes, most importantly cardiac semilunar valvulogenesis. We have screened this gene for mutations in 96 familial and sporadic, well-characterised NS patients and identified 15 different missense mutations in a total of 32 patients (33%), including 23 index patients. Most changes clustered in one exon which encodes parts of the N-SH2 domain. Five of the mutations were recurrent. Interestingly, no mutations in the PTPN11 gene were detected in five additional patients with cardio-facio-cutaneous (CFC) syndrome, which shows clinical similarities to NS.

Mutations in NSD1 are responsible for Sotos syndrome, but are not a frequent finding in other overgrowth phenotypes

Recently, deletions encompassing the nuclear receptor binding SET-Domain 1 (NSD1) gene have been described as the major cause of Japanese patients with the Sotos syndrome, whereas point mutations have been identified in the majority of European Sotos syndrome patients. In order to investigate a possible phenotype–genotype correlation and to further define the predictive value of NSD1 mutations, we performed mutational analysis of the NSD1 gene in 20 patients and one familial case with Sotos syndrome, five patients with Weaver syndrome, six patients with unclassified overgrowth/mental retardation, and six patients with macrocephaly/mental retardation. We were able to identify mutations within the NSD1 gene in 18 patients and the familial case with Sotos syndrome (90%). The mutations (six nonsense, eight frame shifts, three splice site, one missense, one in-frame deletion) are expected to result in an impairment of NSD1 function. The best correlation between clinical assessment and molecular results was obtained for the Sotos facial gestalt in conjunction with overgrowth, macrocephaly, and developmental delay. In contrast to the high mutation detection rate in Sotos syndrome, none of the patients with Weaver syndrome, unclassified overgrowth/mental retardation and macrocephaly/mental retardation, harbored NSD1 mutations. We tested for large deletions by FISH analysis but were not able to identify any deletion cases. The results indicate that the great majority of patients with Sotos syndrome are caused by mutations in NSD1. Deletions covering the NSD1 locus were not found in the patients analyzed here.

Cardio-facio-cutaneous (CFC) syndrome — a distinct entity? Report of three patients demonstrating the diagnostic difficulties in delineation of CFC syndrome

We report on three patients with probable cardio‐facio‐cutaneous (CFC) syndrome. They present clinical findings of this condition such as: growth failure, heart defects, typical craniofacial appearance, ectodennal abnormalities, and developmental delay. We also give a detailed review of the previously published articles on CFC syndrome and discuss the differences between CFC, Noonan, and Costello syndromes. Other differential diagnoses are considered.

Unexpected high frequency of de novo unbalanced translocations in patients with Wolf-Hirschhorn syndrome (WHS)

Editor—Wolf-Hirschhorn syndrome (WHS), first described independently in 1965 by Wolf et al 1 and Hirschhorn et al ,2 is a well defined multiple congenital anomalies/mental retardation syndrome resulting from deletion involving chromosomal band 4p16.3 with a minimal critical region of 165 kb.3 Different mechanisms are responsible for WHS, including terminal 4p deletions, familial translocations, and de novo complex chromosomal rearrangements such as unbalanced translocations. The frequency of translocations in WHS as a result of parental chromosomal translocations is estimated to be 5 to 13%,4 5 whereas the rate of sporadic translocations in WHS was suggested to be 1.6% (2/120).5 A few isolated cases with de novo translocations5-12 resulting in WHS have been described recently. The trisomic segment, however, often could not be defined owing to the lack of specific cytogenetic techniques.5 6 8 13-15 Here we report six patients with unbalanced translocations, t(4p;8p) and t(4p;7p), respectively, and discuss their phenotypic abnormalities. Since 1996 we have performed clinical, molecular, cytogenetic, and molecular-cytogenetic investigations in a total of 22 patients with clinical signs of Wolf-Hirschhorn syndrome. These patients were all seen by one of the authors. In five of them (22%), the combination of cytogenetic and molecular investigations showed a de novo unbalanced translocation; in a sixth patient the de novo occurrence of the translocation could not be confirmed because no blood sample from the father was available. The clinical findings of patients 1-5, who all presented with characteristic features of WHS, are summarised in table 1. Patient 6 (CL220585/87E1624) had some additional findings listed in table1. View this table: Table 1 Clinical findings in patients 1-5 with t(4;8) and patient 6 with t(4;7) The combination of Hirschsprung disease and hydrocephalus was suggestive of CRASH syndrome in patient 6, but SSCP analysis of the L1CAM gene …

EEC syndrome without ectrodactyly? Report of 8 cases.

Eight cases are presented from two families with a variable manifestation of the EEC syndrome. In the first family only one of three affected persons suffers from limb defects. In the second family all five affected have a different pattern of symptoms and only two of them show limb defects. The described families as well as at least one literature report confirm that ectrodactyly is not an obligate symptom of the EEC syndrome.

De Barsy syndrome—an autosomal recessive, progeroid syndrome

We report two families with seven siblings with de Barsy syndrome. Characteristic features include severe mental retardation, hypermobility with athetoid movements, grimacing, muscular hypotonia, laxity of small joints and brisk deep tendon reflexes, progeroid aspect with cutis laxa, atrophy of skin with hyperpigmentation, isolated depigmentations, reduction of subcutaneous fatty tissue, translucent vein pattern, short stature, frontal bossing in the young child, large prominent ears with dysplastic helices and corneal coulding or cataracts. The syndrome probably has autosomal recessive inheritance.

The weaver syndrome: A rare type of primordial overgrowth

A boy with primordial overgrowth, macrocephaly, and anomalies of the face, nails, feet and skeleton is reported. Two cases in the literature—referred to as Weaver syndrome—exhibited nearly identical anomalies. All three cases were sporadic. Main symptoms of the Weaver syndrome are increased birth weight, early overgrowth, macrocephaly, accelerated osseous maturation, typical facies, hoarse, low pitched voice, hypertonia of muscles and mild developmental delay. Further symptoms are thin, deep-set nails, talipes equinovarus, widened distal femora, and some minor abnormalities. A second boy with primordial overgrowth and macrocephaly demonstrated some, but not all, the symptoms of this syndrome. Whether this boy showed a milder expression of the Weaver syndrome or benign familial macrocephaly is discussed.

Familial arhinia, choanal atresia, and microphthalmia

We describe two females (aunt and niece) with variable manifestations of arhinia, choanal atresia, microphthalmia, and hypertelorism. In the literature there is only one report on this syndrome in sibs. We hypothesize autosomal dominant inheritance with reduced penetrance.