p63 mutations have been associated with EEC syndrome (ectrodactyly, ectodermal dysplasia, and cleft lip/palate), as well as with nonsyndromic split hand-split foot malformation (SHFM). We performed p63 mutation analysis in a sample of 43 individuals and families affected with EEC syndrome, in 35 individuals affected with SHFM, and in three families with the EEC-like condition limb-mammary syndrome (LMS), which is characterized by ectrodactyly, cleft palate, and mammary-gland abnormalities. The results differed for these three conditions. p63 gene mutations were detected in almost all (40/43) individuals affected with EEC syndrome. Apart from a frameshift mutation in exon 13, all other EEC mutations were missense, predominantly involving codons 204, 227, 279, 280, and 304. In contrast, p63 mutations were detected in only a small proportion (4/35) of patients with isolated SHFM. p63 mutations in SHFM included three novel mutations: a missense mutation (K193E), a nonsense mutation (Q634X), and a mutation in the 3' splice site for exon 5. The fourth SHFM mutation (R280H) in this series was also found in a patient with classical EEC syndrome, suggesting partial overlap between the EEC and SHFM mutational spectra. The original family with LMS (van Bokhoven et al. 1999) had no detectable p63 mutation, although it clearly localizes to the p63 locus in 3q27. In two other small kindreds affected with LMS, frameshift mutations were detected in exons 13 and 14, respectively. The combined data show that p63 is the major gene for EEC syndrome, and that it makes a modest contribution to SHFM. There appears to be a genotype-phenotype correlation, in that there is a specific pattern of missense mutations in EEC syndrome that are not generally found in SHFM or LMS.

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.

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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.

Synpolydactyly (SPD) is a dominantly inherited congenital limb malformation. Typical cases have 3͞4 finger and 4͞5 toe syndactyly, with a duplicated digit in the syndactylous web, but incomplete penetrance and variable expressivity are common. The condition has recently been shown to be caused by expansions of an imperfect trinucleotide repeat sequence encoding a 15-residue polyalanine tract in HOXD13. We have studied 16 new and 4 previously published SPD families, with between 7 and 14 extra residues in the tract, to analyze the molecular basis for the observed variation in phenotype. Although there is no evidence of change in expansion size within families, even over six generations, there is a highly significant increase in the penetrance and severity of phenotype with increasing expansion size, affecting both hands (P ‫؍‬ 0.012) and feet (P < 0.00005). Affected individuals from a family with a 14-alanine expansion, the largest so far reported, all have a strikingly similar and unusually severe limb phenotype, involving the first digits and distal carpals. Affected males from this family also have hypospadias, not previously described in SPD, but consistent with HOXD13 expression in the developing genital tubercle. The remarkable correlation between phenotype and expansion size suggests that expansion of the tract leads to a specific gain of function in the mutant HOXD13 protein, and has interesting implications for the role of polyalanine tracts in the control of transcription.Dominantly inherited disorders frequently display incomplete penetrance (a normal phenotype in some mutation carriers) and variable expressivity (different degrees of phenotypic severity in affected individuals), the molecular basis for which is generally not understood. One such disorder is the rare dominantly inherited congenital limb malformation, synpolydactyly (SPD; OMIM No. 186000). Mutations in the first exon of HOXD13 have recently been found in three American SPD families (1), expanding a 15-residue polyalanine tract encoded by an imperfect trinucleotide repeat sequence by 7, 8, and 10 additional residues, respectively. Similar 9-residue expansions subsequently have been reported in two Turkish SPD families (2). SPD typically consists of 3͞4 finger and 4͞5 toe syndactyly, with a duplicated digit in the syndactylous web (3). Incomplete penetrance and variable expressivity both between and within affected families are common (4-6). From one to four limbs can be involved, and the severity of involvement ranges from partial skin syndactyly to complete reduplication of a digit, extending as far proximally as the metacarpals͞tarsals. Associated distal limb abnormalities include fifth-finger clinodactyly, camptodactyly, or brachydactyly; variable syndactyly of the second to fifth toes; and middle phalanx hypoplasia͞ aplasia.To investigate the molecular basis for this incomplete penetrance and variable expressivity, we analyzed the genotype and phenotype of 16 new SPD pedigrees, including one with an expansion that almost doub...

The spontaneous growth of 150 patients with Turner syndrome from three German centers--90 with 45,X0 constitution, 60 with other chromosomal abnormalities--has been analyzed. The mean adult height was found to be (n = 14) 146.8 cm. It was observed that growth in these patients can be divided into four phases: (1) Intrauterine growth, which is retarded; (2) Height development, which is normal up to a bone-age of about 2 years; (3) Between a bone-age of 2 and 11 years when stunting of growth is most marked; (4) After a bone-age of 11 years--the time at which puberty should normally start--the growth phase is prolonged, but total height gain is only little below normal levels. No difference in height could be observed between cases with X0 karyotype and other chromosomal variants. The data are compared with those in the literature.

The literature dealing with the Seckel syndrome is discussed critically. Some 60 patients have been published as having the Seckel syndrome. The diagnostic criteria proposed by Seckel are met by only 1/3 of these. It seems evident that this "syndrome" is a heterogeneous group of microcephalic primordial dwarfism. An approach to the delineation of the Seckel syndrome is given.

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