X-linked recessive inheritance of radial ray deficiencies in a family with four affected males.

Radial ray deficiencies are frequently associated with additional clinical anomalies and have a heterogeneous aetiology. X-linked forms are extremely rare. We report a family in which four male relatives show bilateral absence of the radius with presence of the thumbs and associated anomalies. The segregation of the phenotype is suggestive for X-linked recessive inheritance. This is confirmed by performing linkage analysis using 24 markers spanning the X chromosome in which a maximum lod score of 1.93 for DXS8067 and DXS1001 is obtained. We defined a critical region of maximal 16.2 cM on the X chromosome with haplotype analysis.

Anophthalmos-syndactyly (Waardenburg) syndrome without oligodactyly of toes.

We report on 2 brothers from a consanguineous family from a small city of southeast Turkey. Both have bilateral anophthalmia, soft tissue syndactyly of the feet, bilateral partial synostosis of metatarsals IV and V, and basal synostosis of the fourth and fifth toes on the right in the older sib only, thus differing from all previously reported cases of anophthalmos-syndactyly syndrome.

Phenotypic variability of triphalangeal thumb-polysyndactyly syndrome linked to chromosome 7q36.

Triphalangeal thumb-polysyndactyly (TPT-PS) is an isolated limb malformation consisting of pre- and postaxial polysyndactyly of hands and feet. The only family reported so far is of Dutch origin, and the genetic mapping study localized the TPT-PS locus at chromosome region 7q36 where the isolated triphalangeal thumb (TPT) anomaly has also been mapped. It was suggested that TPT-PS is a phenotypic variation of isolated TPT, and the same ancestral mutation may produce both phenotypes. Here we report on the second family with this malformation from the Turkish population. The characteristic findings in this family are triphalangeal thumb, webbing between 3rd, 4th, and 5th fingers associated with bony synostosis in the distal phalanges of the same fingers, and pre- and postaxial polysyndactyly of feet. Some individuals show a more severe phenotype with a complete syndactyly of all fingers giving a "cup-like" appearance to the hands. Genetic linkage study with DNA markers D7S1823, D7S550, D7S559, and D7S2423 demonstrated that this family is also linked to chromosome band 7q36. Identification of a second family from a distinct ethnic background suggests that TPT-PS and isolated TPT are not caused by the same ancestral mutation as it was originally anticipated.

A clinically variant fibrosis syndrome in a Turkish family maps to the CFEOM1 locus on chromosome 12.

OBJECTIVES: To describe the phenotype of a Turkish family with variably expressed congenital fibrosis of the extraocular muscles (CFEOM), and to determine the genetic location of their disorder. METHODS: Participants were examined and had blood extracted for genetic analysis. The clinical features of the family's disorder were studied, and the disorder was tested for linkage to the 3 known CFEOM loci (CFEOM1, CFEOM2, and CFEOM3). RESULTS: Twenty-nine affected and 31 unaffected family members participated in the study. Eighteen affected individuals had congenital bilateral ptosis and restrictive infraductive (downward) ophthalmoplegia, consistent with the published descriptions of classic CFEOM families linked to the CFEOM1 locus. Eleven affected individuals, however, had eye(s) in a neutral primary position, residual upgaze, and/or absence of ptosis, thus deviating from previous descriptions of CFEOM1-linked families. Analysis of the autosomal dominant variably expressed disorder in this family revealed linkage to the CFEOM1 locus on chromosome 12 with a maximum lod score of 10.8 at D12S85. CONCLUSIONS: This Turkish family segregates a variably expressed form of CFEOM that most closely resembles CFEOM3-linked CFEOM, but maps to the CFEOM1 locus. CLINICAL RELEVANCE: These data establish that there is much greater phenotypic heterogeneity at the CFEOM1 locus than previously reported, and this may blur our ability to distinguish the different CFEOM loci based solely on clinical presentation. Arch Ophthalmol. 2000;118:1090-1097

BIGH3 gene analysis in the differential diagnosis of corneal dystrophies.

PURPOSE: To identify the mutation in the keratoepithelin gene for proper diagnosis of granular corneal dystrophies. METHODS: Four generations of a single family with corneal dystrophy were analyzed. Fourteen family members were examined and 11 were found to be affected by clinical evaluation. Genetic DNA was extracted from proband's leukocytes for molecular analysis. Exons 4 and 12 of the BIGH3 gene were amplified then directly sequenced. RESULTS: The clinical appearance of corneas consisted of grayish white granules with sharp borders, fine dots, and radial lines in the superficial part of the central corneal stroma, which resembles granular and Avellino corneal dystrophies. Performing BIGH3 gene analysis, we observed a C-to-T transition at position 1710 (CGG to TGG) producing R555W mutation, which is a hot spot for granular corneal dystrophy. CONCLUSION: Direct clinical examination may be insignificant in the proper diagnosis of corneal dystrophies, and molecular genetic approach may be required.

Nasopalpebral lipoma-coloboma syndrome.

An autosomal dominant dysplasia-malformation syndrome affecting seven individuals in one family is reported. The components of the syndrome include congenital nasopalpebral lipoma, telecanthus, and bilateral colobomas of upper and lower lids without midface hypoplasia. It appears to be the second recorded example resulting from an autosomal dominant gene fully penetrant in both sexes.

Identification of three different truncating mutations in cytochrome P4501B1 (CYP1B1) as the principal cause of primary congenital glaucoma (Buphthalmos) in families linked to the GLC3A locus on chromosome 2p21.

Primary congenital glaucoma (Buphthalmos) is an autosomal recessive eye disorder, postulated to result from developmental defects in the anterior eye segment. Previously, we reported two chromosomal locations for this condition on 2p21 (GLC3A) and 1p36 (GLC3B) respectively. In this study, heritable mutations of human cytochrome P4501B1 gene (CYP1B1) in affected individuals of five well-characterized families linked to the GLC3A locus are described. CYP1B1 gene has previously been mapped within the GLC3A candidate region and its expression in the trabecular meshwork cells has been demonstrated in this study. Three different homozygous mutations were identified and characterized: a 13 bp deletion in exon III; an insertion of a single cytosine base in exon II; and a larger deletion affecting the 5' end of exon III and the adjacent intronic region. All of these are frameshift mutations that are predicted to remove domains essential for the function of the CYP1B1 protein. Therefore, it is expected that all these mutations result in functional null alleles. The mutations detected in the affected members of these families were not present in 470 chromosomes from randomly selected normal individuals, thus strongly suggesting that CYP1B1 is the gene for the GLC3A locus on 2p21. The results are discussed in the context of the earlier hypothesis that 'drug-metabolizing' enzymes might modulate the processes of growth and differentiation by controlling the steady-state-levels of oxygenated growth-effector molecules.

Localization of the syndactyly type II (synpolydactyly) locus to 2q31 region and identification of tight linkage to HOXD8 intragenic marker.

Syndactyly type II (SynPolyDactyly; SPD) is an autosomal dominant condition with incomplete penetrance and variable expressivity. Sixty-two meioses from a kindred with 425 individuals were used to map the SPD locus to 2q31 region, approximately 1.7 cM (Lod score = 12.96) centromeric to HOXD8 intragenic marker. Other homeobox-containing genes in this region have previously been ordered as cen-DLX1/DLX2-EVX2-(5' --> HOXD13..HOXD8.HOXD1 --> 3')-tel')-tel. A single recombinant with HOXD8 excluded the most 3' end of HOXD cluster as a candidate site for SPD, but a mutation in the 5' end of HOXD cluster, especially in HOXD13, EVX2 or DLX2/DLX1, may still be responsible for this phenotype. An updated order of D2S142-D2S111-(D2S335/D2S333)-D2S326-D2 S1238-SPD- (HOXD8/D2S1244)-(D2S300/D2S138)-D2S148- D2S324- D2S1384-D2S434 [sequence:see text] was deduced from meiotic recombination events.

Genomic structure of HOXD13 gene: a nine polyalanine duplication causes synpolydactyly in two unrelated families.

Synpolydactyly (SPD) is a limb malformation that shows a characteristic manifestation in both hands and feet. This condition is inherited as an autosomal dominant trait with reduced penetrance. We have recently mapped this locus centromeric to the HOXD8 intragenic marker and suggested the HOXD13 gene as a potential candidate for this condition. The genomic structure of HOXD13 established in this study consists of two exons that encodes a polypeptide of 335 amino acids. The downstream exon at the 3' end of this gene contains the homeodomain sequences that are highly conserved. Sixty-three bp upstream of this exon lies a stretch of intronic CA-repeats that proved to be polymorphic in two different populations. The upstream exon encodes 75% of the entire protein and contains a stretch of 15 normal alanines at its 5' end. Sequence comparison at this position in the homozygous affected individuals identified a total of 24 alanine residues that resulted from a duplication of nine polyalanines. In two unrelated SPD families, this duplication was directly transmitted from the affected parents to their affected, but not unaffected, offspring; in one family its size has remained constant for at least 150 years spanning over seven generations. The presence of this duplication confirmed the status of four normal gene carriers, one incomplete penetrance and two affected individuals who were recombinants for HOXD8 or HOXD13-CA repeat markers. This duplication was not present in 150 chromosomes of unrelated healthy subjects of two different populations.

Genetic linkage study of familial Mediterranean fever (FMF) to 16p13.3 and evidence for genetic heterogeneity in the Turkish population.

Familial Mediterranean fever (FMF) is an autosomal recessive condition that is almost entirely restricted to the non-Askhenazi Jews, Arabs, Armenians, and Turks. Genetic linkage study of a large group of non-Turkish families has previously mapped the FMF locus to the 16p13.3 region and shown that this locus resides 0.305 cM distal to D16S246. Furthermore, allelic association has also been shown with D16S3070 (75%) and D16S3275 (66%). However, no genetic heterogeneity has been described for any of the three major reported groups of FMF families. Here, we describe the genetic linkage relationship of the fourth major group of Turkish families and report the first evidence for genetic heterogeneity of this condition. Two point linkage analysis and haplotype inspection of 15 DNA markers from the reported region of the FMF locus identified tight linkage in a group of six Turkish FMF families. A maximum lod score of 9.115 at theta = 0.00 was observed for D16S3024. Nine other DNA markers provided similar evidence of linkage with lod score values of above 5.21. However, two other FMF families were completely unlinked to this region of chromosome 16. Haplotype construction of DNA markers in five consanguineous linked families showed that a segment of homozygosity has been conserved for D16S3070 and D16S2617. No other DNA markers showed any such conservation. Therefore, we suggested that these two markers reside in close proximity to the FMF locus. Furthermore, we observed 80% allelic association with D16S2617 but no association with D16S3070 or any other DNA markers from the FMF critical region. In summary, we conclude that our Turkish families are also linked to the reported FMF locus at 16p13.3, there is a genetic heterogeneity for this condition at least in our group of Turkish families, and D16S2617 is in linkage disequilibrium in the Turkish FMF families. Combination of this study with previously published observations suggests that the FMF locus resides between D16S246 and D16S3070/D16S2617 and within a region of about 250-300 kb.

A large Turkish kindred with syndactyly type II (synpolydactyly). 1. Field investigation, clinical and pedigree data.

A very large Turkish family with syndactyly type II (synpolydactyly (SPD)) is described, which originated from and is mainly concentrated in the village of Derbent, Afyon. The kindred consists of 425 subjects over seven generations, of whom 182 are affected. It appears that a founder effect in this village has led to this extensive kindred. This condition is inherited as an autosomal dominant trait with variable expressivity and an estimated penetrance of 96%. Penetrance is different between the upper (96%) and lower (69.5%) extremities. No excess of affected males or females or other associated features were documented in this condition. Variations in the involvement of one or both hands, upper or lower extremities, bone and soft tissue, as well as variation in the affected subjects of two successive generations were documented. We also noted that metacarpal and metatarsal involvement and middle phalangeal hypoplasia of the feet are the consistent features of SPD and, therefore, should be considered as characteristic of this phenotype. We observed four different phenotypes in various branches of the Derbent kindred: (1) subjects presenting typical features of SPD; (2) subjects exhibiting both pre- and post-axial polydactyly simultaneously; (3) persons manifesting postaxial polydactyly type A; and (4) subjects born to two affected parents with severe hand and foot deformities that have not been previously described in any other SPD families (that is, homozygotes). A total of 27 affected offspring were born to two such affected parents, of whom seven are expected to be homozygous for the SPD gene. This group is presented in an accompanying paper in this issue of the Journal. A molecular study is currently under way to identify the chromosomal location of the defective gene.

A large Turkish kindred with syndactyly type II (synpolydactyly). 2. Homozygous phenotype?

Syndactyly type II (synpolydactyly (SPD)) is an autosomal dominant condition with typical abnormalities of the distal parts of both upper and lower limbs. We report here a previously undescribed phenotypic feature of people with severe hand and foot deformities who were born to two affected parents. This is the first example of SPD subjects manifesting a very distinctive phenotype, suggesting that they must be homozygous for this condition. The typical characteristic clinical features in these subjects are as follows: (1) short hands with wrinkled fatty skin and short feet; (2) complete soft tissue syndactyly involving all four limbs; (3) polydactyly of the preaxial, mesoaxial, and postaxial digits of the hands; (4) loss of the normal tubular shape of the carpal, metacarpal, and phalangeal bones, so as to give polygonal structures; (5) loss of the typical structure of the cuboid and all three cuneiform bones while the talus calcaneus and navicular bones remain intact; (6) large bony islands instead of metatarsals, most probably because of cuboid-metatarsal and cuneiform-metatarsal fusions; and (7) severe middle phalangeal hypoplasia/aplasia as well as fusion of some phalangeal structures that are associated with the loss of normal phalangeal pattern. We report seven subjects with this phenotype from three different branches of a very large SPD pedigree exhibiting the same phenotype with minimal variation. In mice, the Polysyndactyly (Ps) mutation shows a pattern of synpolydactyly very similar to that of human SPD, suggesting that they may well be homologous mutations. A molecular genetic study is currently under way to determine the chromosomal location of the SPD locus in humans and to identify the corresponding homologous region in mice.

Mesoaxial complete syndactyly and synostosis with hypoplastic thumbs: an unusual combination or homozygous expression of syndactyly type I?

Syndactyly type I is an autosomal dominant condition with complete or partial webbing between the third and fourth fingers or the second and third toes or both. We report here a previously undescribed phenotype of severe mesoaxial syndactyly and synostosis in patients born to affected parents. The characteristic features of these severe cases are (1) complete syndactyly and synostosis of the third and fourth fingers; (2) severe bone reduction in the proximal phalanges of the same fingers; (3) hypoplasia of the thumbs and halluces; (4) aplasia/hypoplasia of the middle phalanges of the second and fifth fingers; and (5) complete or partial soft tissue syndactyly of the toes. We report on three offspring with this phenotype from two different branches of a syndactyly type I family, suggesting that they may be homozygous for this condition. SSCP and linkage analysis indicated that neither HOXD13 nor other relevant genes in the chromosome 2q31 region was responsible for this phenotype.

Clinical observations in autosomal recessive spastic paraplegia in childhood and further evidence for genetic heterogeneity.

Among our 23 families (32 cases) with autosomal recessive hereditary spastic paraplegia (AR-HSP) all presenting in childhood, 9 families had the "pure" form. Occasional patients with this form had upper extremity hyperreflexia, pes cavus and sphincter disturbances, even at the early stages. Fourteen families were classified as the "complicated" types which manifested with mental retardation and cerebellar abnormalities. The evolution and severity was variable, but was generally consistent within families. Carriers (parents) did not manifest any signs. A total of 5 multiplex families with "complicated" type were used to test for a genetic heterogeneity to the region on chromosome 8p12-q13 where the "pure" AR-HSP has been mapped previously. No evidence in favor of linkage was detected in 3 of our families, thus we further supported genetic heterogeneity for AR-HSP.

DACH: genomic characterization, evaluation as a candidate for postaxial polydactyly type A2, and developmental expression pattern of the mouse homologue.

The gene DACH is a human homologue of Drosophila melanogaster dachshund (dac), which encodes a nuclear factor essential for determining cell fates in the eye, leg, and nervous system of the fly. To investigate possible connections between DACH and inherited developmental disorders, we have characterized the human DACH genomic structure and investigated the tissue and cellular distribution of the mouse DACH1 protein during development. DACH spans 400 kb and is encoded by 12 exons. The predominant DACH transcript is 5.2 kb and encodes a 706-amino-acid protein with an observed molecular weight of 97 kDa.DACH mRNA was detected in multiple adult human tissues including kidney and heart. The mouse DACH1 protein was immunolocalized to specific cell types within the developing kidneys, eyes, cochleae, and limb buds. Data suggest genetic linkage of the limb bud patterning defect postaxial polydactyly type A (designated PAP-A2, MIM 602085) to a 28-cM interval on chromosome 13 that includes DACH. However, mutation analysis of DACH in this PAP-A2 pedigree revealed no sequence differences in the coding region, splice sites, or proximal promoter region. The data presented will allow for the analysis of DACH as a candidate for other developmental disorders affecting the limbs, kidneys, eyes, ears, and other sites of DACH expression.

Assignment of a locus (GLC3A) for primary congenital glaucoma (Buphthalmos) to 2p21 and evidence for genetic heterogeneity.

Primary congenital glaucoma (GLC3) is an inherited eye disorder that accounts for 0.01-0.04% of total blindness. Although a large number of chromosomal abnormalities have already been reported in patients with congenital glaucoma, the precise location and pathogenesis of this condition remain elusive. By using a group of 17 GLC3 families and a combination of both candidate regional and general positional mapping strategies, we have mapped a locus for GLC3 to the short arm of chromosome 2. Eleven families showed no recombination with 3 tightly linked markers of D2S177 (Z = 9.40), D2S1346 (Z = 8.83), and D2S1348 (Z = 8.90) with a combined haplotype lod score of 11.50. Haplotype and multipoint linkage analyses of 14 DNA markers from 2p indicated that the disease gene is located in the 2p21 region and is flanked by DNA markers D2S1788/D2S1325 (theta = 0.03; Z = 5.42) and D2S1356 (theta = 0.05; Z = 4.69). Inspection of haplotype and heterogeneity analysis confirmed that 6 families are not linked to the 2p21 region, thus providing the first proof of genetic heterogeneity for this phenotype. We therefore designated the locus on 2p21 GLC3A and positioned it in the overall linkage map of Tel-D2S405-D2S367-(D2S1788/D2S1325)-[(GLC3A++ +, D2S177)/(D2S1346/D2S1348)]-D2S1356-D2S119- D2S1761-D2S1248-D2S1352-D2S406- D2S441-Cen. Of the seven genes mapping to the 2p21 region, CAD, CALM2, and LHCGR are centromeric to D2S119 and can be excluded as a candidate for GLC3A, but mutations in PRKR, TIK, SOS1, or SPTBN1 may still be accountable for this phenotype. As human 2p21 shows homology with mouse chromosomes 11 and 17, the homolog of GLC3A is expected to reside on one of these two chromosomes.

A second locus (GLC3B) for primary congenital glaucoma (Buphthalmos) maps to the 1p36 region.

Primary congenital glaucoma (gene symbol: GLC3) is an ocular disorder that occurs for 0.01-0.04% of blind people. In the majority of familial cases reported so far, this condition is inherited as an autosomal recessive trait. We have recently used a group of 17 GLC3 families with a minimum of two affected offspring and consanguinity in most of the parental generation and mapped the first GLC3 locus (GLC3A) to the 2p21 region. Six families did not show any linkage to the GLC3A locus and thus provided evidence for genetic heterogeneity of this disorder. A total of eight families unlinked to the 2p21 region were used to search for the chromosomal location of the second GLC3 locus. Herein, we describe mapping of a new locus (designated GLC3B) for primary congenital glaucoma to the short arm of chromosome 1 (1p36.2-36.1) that is situated centromeric to the neuroblastoma and Charcot-Marie-Tooth type 2A (CMT2A) loci. A total of 17 DNA markers were genotyped from this region of chromosome 1. Four families showed no recombination with the two markers D1S2834 and D1S402 with a maximum lod score of 4.510 and 4.157 respectively. Pairwise and multipoint linkage analysis and inspection of the haplotypes revealed that the remaining four families are not linked to this part of chromosome 1, thus providing further evidence that at least one more locus for the autosomal recessive form of GLC3 must exist in the genome. Based on the recombination events, the overall linkage map of this region is: tel-D1S1192-D1S1635-D1S1193 - (D1S1597/-D1S489/D1S228)- [GLC3B/D1S2834/D1S402] - (D1S1176/D1S507/D1S407) - D1S2728-(MFAP2/D1S170) - D1S1368 - D1S436-D1S1592-cen.

Sequence analysis and homology modeling suggest that primary congenital glaucoma on 2p21 results from mutations disrupting either the hinge region or the conserved core structures of cytochrome P4501B1.

We recently reported three truncating mutations of the cytochrome P4501B1 gene (CYP1B1) in five families with primary congenital glaucoma (PCG) linked to the GLC3A locus on chromosome 2p21. This could be the first direct evidence supporting the hypothesis that members of the cytochrome P450 superfamily may control the processes of growth and differentiation. We present a comprehensive sequence analysis of the translated regions of the CYP1B1 gene in 22 PCG families and 100 randomly selected normal individuals. Sixteen mutations and six polymorphisms were identified, illustrating an extensive allelic heterogeneity. The positions affected by these changes were evaluated by building a three-dimensional homology model of the conserved C-terminal half of CYP1B1. These mutations may interfere with heme incorporation, by affecting the hinge region and/or the conserved core structures (CCS) that determine the proper folding and heme-binding ability of P450 molecules. In contrast, all polymorphic sites were poorly conserved and located outside the CCS. Northern hybridization analysis showed strong expression of CYP1B1 in the anterior uveal tract, which is involved in secretion of the aqueous humor and in regulation of outflow facility, processes that could contribute to the elevated intraocular pressure characteristic of PCG.