Mowat-Wilson syndrome: facial phenotype changing with age: study of 19 Italian patients and review of the literature.

Mowat-Wilson syndrome (MWS; OMIM #235730) is a genetic condition caused by heterozygous mutations or deletions of the ZEB2 gene, and characterized by typical face, moderate-to-severe mental retardation, epilepsy, Hirschsprung disease, and multiple congenital anomalies, including genital anomalies (particularly hypospadias in males), congenital heart defects, agenesis of the corpus callosum, and eye defects. Since the first delineation by Mowat et al. [Mowat et al. (1998); J Med Genet 35:617-623], approximately 179 patients with ZEB2 mutations, deletions or cytogenetic abnormalities have been reported primarily from Europe, Australia and the United States. Genetic defects include chromosome 2q21-q23 microdeletions (or different chromosome rearrangements) in few patients, and ZEB2 mutations in most. We report on clinical and genetic data from 19 Italian patients, diagnosed within the last 5 years, including six previously published, and compare them with patients already reported. The main purpose of this review is to underline a highly consistent phenotype and to highlight the phenotypic evolution occurring with age, particularly of the facial characteristics. The prevalence of MWS is likely to be underestimated. Knowledge of the phenotypic spectrum of MWS and of its changing phenotype with age can improve the detection rate of this condition.

Holt-Oram syndrome associated with anomalies of the feet.

Holt-Oram syndrome (HOS) (OMIM 142900) is characterized by upper-extremity malformations involving the radial, thenar, or carpal bones and a personal and/or family history of congenital heart defects (CHDs). It is inherited in an autosomal dominant manner. The TBX5 gene located on chromosome 12 (12q24.1) is the only gene currently known to be associated with HOS and is associated with variable phenotypes. We report on the clinical and molecular characterization of a HOS family with three affected individuals and a novel mutation (Lys88ter). We discuss genotype-phenotype correlations, the presence of foot anomalies in one affected individual, and the role of atypical features in HOS differential diagnosis.

Incidence of ocular pathologies in Italian children with Down syndrome.

PURPOSE: This study identifies the incidence of primary ocular pathologies in a population of Italian children with Down syndrome. METHODS: A total of 157 Italian children with Down syndrome, age between 1 month and 18 years, were screened between February 2005 and October 2006. The ophthalmologic evaluation included a global inspection of orbit and bulbus oculi, evaluation of ocular motility and visual acuity, slit lamp biomicroscopy, cycloplegic skiascopy, tonometry, and indirect ophthalmoscopy. RESULTS: The overall incidence of ocular abnormalities was epicanthal fold (132 patients, 84%), hyperopia (93 patients, 59%), astigmatism (44 patients, 28%), myopia (14 patients, 9%), strabismus (56 patients, 36%, 45 cases of esotropia and 11 cases of exotropia), congenital nasolacrimal duct obstruction (35 patients, 22%), cataract (18 patients, 11%), nystagmus (9 patients, 6%), blepharitis and conjunctivitis (6 patients, 4%), and retinal anomalies (10 patients, 6%). Unlike previous reports in patients with Down syndrome, no congenital glaucoma, keratoconus, or Brushfield spots were observed. CONCLUSIONS: Compared to other studies in patients with Down syndrome, we observed a higher incidence of hyperopia and a lower incidence of myopia. The incidence of nystagmus, blepharitis,and conjunctivitis was less than that reported in other studies, while strabismus, especially exotropia (20%), had a high incidence in our cohort. We also frequently observed obstruction of the nasolacrimal duct (22%), but no keratoconus or glaucoma.

Inv dup del (1)(pter-->q44::q44-->q42:) with the classical phenotype of trisomy 1q42-qter.

We report on a girl with a trisomy 1q42-q44 due to an inverted duplication of this region, associated with a terminal deletion of the long arm of the rearranged chromosome 1. Both the large duplication (more than 30 cM) and the small deletion were detected by FISH. Complete karyotype was: (46,XX, inv dup(1)(q44q42).ish(dup del 1)(q44q42)(D1S446x2, D1S423x2, tel1q-). The phenotype of the patient is characterized by macrocephaly with prominent forehead, downslanting palpebral fissures, micrognathia, and psychomotor retardation. All these clinical features are the same as observed for the typical trisomy 1q42-qter syndrome. The phenotypic effects of the inversion and the terminal deletion of 1q in addition to the trisomy are discussed here.

Case of Myhre syndrome with autism and peculiar skin histological findings.

Myhre syndrome (MS) (MIM 139210) is a rare disorder characterized by short stature, mental retardation, muscular build, blepharophimosis, and decreased joint mobility. We report on a 14-year-old boy with clinical findings consistent with a diagnosis of Myhre syndrome, associated with autism and peculiar skin histological findings.

The molecular bases of cystinuria and lysinuric protein intolerance.

Cystinuria and lysinuric protein intolerance are inherited aminoacidurias caused by defective amino-acid transport activities linked to a family of heteromeric amino-acid transporters (HATs). HATs comprise two subunits: co-expression of subunits 4F2hc and y(+)LAT-1 induces the efflux of dibasic amino acids from cells, whereas co-expression of subunits rBAT and b(o,+)AT induces the renal reabsorption and intestinal absorption of cystine and dibasic amino acids at the brush border of epithelial cells. Recently, the role of b(o,+)AT (SLC7A9) in cystinuria (non Type I) and the role of y(+)LAT-1 (SLC7A7) in lysinuric protein intolerance have been demonstrated.

Contribution of the cystathionine beta-synthase gene (844ins68) polymorphism to the risk of early-onset venous and arterial occlusive disease and of fasting hyperhomocysteinemia.

The frequency of the heterozygous 844ins68 mutation of the cystathionine beta-synthase (CBS) gene and of its association with the homozygous C677T transition of the methylenetetrahydrofolate reductase (MTHFR) gene, plasma fasting tHcy, folate and vitamin B12 levels were evaluated in 309 consecutive patients with objectively diagnosed early-onset venous (n = 200) or arterial thromboembolic disease (n = 109) recruited over 25 months in Milan (North Italy) and Naples (South Italy). The above gene polymorphisms were also evaluated in a population of 787 unmatched controls, 204 of whom--similar to patients for age- and sex-distribution--had fasting tHcy, vitamins and activated protein C resistance measured in their plasma. Moderate fasting hyperhomocysteinemia was detected in 15.5% of patients and in 5.9% of 204 controls (Mantel-Haenszel OR after stratification for type of occlusive disease and gender: 2.88; 1.48-5.32). The frequencies of the 677TT mutation of the MTHFR gene and of the heterozygous 844ins68 insertion of the CBS gene were not significantly different in the patient (19.4% and 6.9%) and the control population (16.5% and 7.8%), but the association of the two gene polymorphisms found in 3.9% of patients and in 1.1% of controls - was significantly associated with an increased risk of venous or arterial occlusive diseases (RR = 3.63; 1.48-8.91). The MTHFR 677TT mutation (RR: 6.92; 3.86-12.4) and its association with the 844ins68 insertion (RR: 21.9; 8.35-57.4), but not the isolated insertion (RR: 0.71), were more frequent in patients and controls with fasting hyperhomocysteinemia than in normohomocysteinemic subjects, irrespective of the type of occlusive disease (venous or arterial). When adjusted for determinants of hyperhomocysteinemia in the patient and the control populations (generalized linear model), fasting tHcy levels were significantly higher in subjects with association of the two gene abnormalities (24.2+/-3.8 micromol/L) than in subjects with the MTHFR 677TT mutation only (14.0+/-5.8 micromol/L, p = 0.004). Activated protein C resistance was significantly more prevalent in venous patients (9.9%) than in controls (3.9%, OR = 2.69; 1.08-6.88). Six of 21 venous patients with APC-resistance also had hyperhomocysteinemia (RR = 5.04; 0.68-37.6), but isolated fasting hyperhomocysteinemia retained statistical significance for the association with venous occlusive disease (RR = 2.84; 1.34-6.01). Heterozygosity for the 844ins68 mutation of the CBS gene is not per se a risk factor for premature arterial and/or venous occlusive diseases. However, when detected in combination with thermolabile MTHFR, it increases by almost 4-fold the risk of occlusive diseases (arterial and/or venous), by increasing the risk and the degree of fasting hyperhomocysteinemia.

Arginine transport through system y(+)L in cultured human fibroblasts: normal phenotype of cells from LPI subjects.

In lysinuric protein intolerance (LPI), impaired transport of cationic amino acids in kidney and intestine is due to mutations of the SLC7A7 gene. To assess the functional consequences of the LPI defect in nonepithelial cells, we have characterized cationic amino acid (CAA) transport in human fibroblasts obtained from LPI patients and a normal subject. In both cell types the bidirectional fluxes of arginine are due to the additive contributions of two Na(+)-independent, transstimulated transport systems. One of these mechanisms, inhibited by N-ethylmaleimide (NEM) and sensitive to the membrane potential, is identifiable with system y(+). The NEM- and potential-insensitive component, suppressed by L-leucine only in the presence of Na(+), is mostly due to the activity of system y(+)L. The inward and outward activities of the two systems are comparable in control and LPI fibroblasts. Both cell types express SLC7A1 (CAT1) and SLC7A2 (CAT2B and CAT2A) as well as SLC7A6 (y+LAT2) and SLC7A7 (y+LAT1). We conclude that LPI fibroblasts exhibit normal CAA transport through system y(+)L, probably referable to the activity of SLC7A6/y+LAT2.

Cationic amino acid transport through system y+L in erythrocytes of patients with lysinuric protein intolerance.

We test the hypothesis that lysinuric protein intolerance (LPI), a rare autosomal recessive defect of cationic amino acid transport, results from the absence of the recently described y+L amino acid transporter. We compare fluxes of lysine (1 microM) into erythrocytes of normal subjects with those of patients homozygous for the LPI mutation. No significant differences in fluxes through system y+L in normal or LPI cells were found, excluding the possibility that system y+L cannot be expressed in patients with LPI. Reasons for supposing that there may be tissue-specific processing of two recently described genes encoding the y+L transporter are discussed. Polymerase chain reaction measurement of expression of these two genes in an erythroleukemic cell line suggests that alternatively there may be an as-yet-unidentified additional member of this gene family.

Relaxation of insulin-like growth factor 2 imprinting and discordant methylation at KvDMR1 in two first cousins affected by Beckwith-Wiedemann and Klippel-Trenaunay-Weber syndromes.

Beckwith-Wiedeman syndrome (BWS) and Klippel-Trenaunay-Weber syndrome (KTWS) are different human disorders characterized, among other features, by tissue overgrowth. Deregulation of one or more imprinted genes located at chromosome 11p15.5, of which insulin-like growth factor 2 (IGF2) is the most likely candidate, is believed to cause BWS, whereas the etiology of KTWS is completely obscure. We report a case of BWS and a case of KTWS in a single family. The probands, sons of two sisters, showed relaxation of the maternal IGF2 imprinting, although they inherited different 11p15.5 alleles from their mothers and did not show any chromosome rearrangement. The patient with BWS also displayed hypomethylation at KvDMR1, a maternally methylated CpG island within an intron of the KvLQT1 gene. The unaffected brother of the BWS proband shared the same maternal and paternal 11p15.5 haplotype with his brother, but the KvDMR1 locus was normally methylated. Methylation of the H19 gene was normal in both the BWS and KTWS probands. Linkage between the insulin-like growth factor 2 receptor (IGF2R) gene and the tissue overgrowth was also excluded. These results raise the possibility that a defective modifier or regulatory gene unlinked to 11p15.5 caused a spectrum of epigenetic alterations in the germ line or early development of both cousins, ranging from the relaxation of IGF2 imprinting in the KTWS proband to disruption of both the imprinted expression of IGF2 and the imprinted methylation of KvDMR1 in the BWS proband. Analysis of these data also indicates that loss of IGF2 imprinting is not necessarily linked to alteration of methylation at the KvDMR1 or H19 loci and supports the notion that IGF2 overexpression is involved in the etiology of the tissue hypertrophy observed in different overgrowth disorders, including KTWS.

Structure of the SLC7A7 gene and mutational analysis of patients affected by lysinuric protein intolerance.

Lysinuric protein intolerance (LPI) is a rare autosomal recessive defect of cationic amino acid transport caused by mutations in the SLC7A7 gene. We report the genomic structure of the gene and the results of the mutational analysis in Italian, Tunisian, and Japanese patients. The SLC7A7 gene consists of 10 exons; sequences of all of the exon-intron boundaries are reported here. All of the mutant alleles were characterized and eight novel mutations were detected, including two missense mutations, 242A-->C (M1L) and 1399C-->A (S386R); a nonsense mutation 967G-->A (W242X); two splice mutations IVS3 +1G-->A and IVS6 +1G-->T; a single-base insertion, 786insT; and two 4-bp deletions, 455delCTCT and 1425delTTCT. In addition, a previously reported mutation, 1625insATCA, was found in one patient. It is noteworthy that 242A-->C causes the change of Met1 to Leu, a rare mutational event previously found in a few inherited conditions. We failed to establish a genotype/phenotype correlation. In fact, both intrafamilial and interfamilial phenotypic variability were observed in homozygotes for the same mutation. The DNA-based tests are now easily accessible for molecular diagnosis, genetic counseling, and prenatal diagnosis of LPI.

Smith-Lemli-Opitz syndrome: evidence of T93M as a common mutation of delta7-sterol reductase in Italy and report of three novel mutations.

The Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis characterised by facial dysmorphisms, mental retardation and multiple congenital anomalies. SLOS is caused by mutations of the human Delta7-sterol reductase (DHCR7) gene and, so far, 19 different mutations have been described. Among these, mutations impairing the activity of the C-terminus appear to be the most severe. Here we report the mutational analysis of the DHCR7 gene in nine Italian SLOS patients. The T93M mutation, previously reported in one patient, results the most frequent one (7/18 alleles) in our survey. Furthermore, we identified three novel mutations, two missense mutations (N407Y and E448K), and a 33 bp deletion spanning part of exon 5 and the donor splice site of intron 5.

SLC7A8, a gene mapping within the lysinuric protein intolerance critical region, encodes a new member of the glycoprotein-associated amino acid transporter family.

Using a bioinformatic approach, we have identified a new transcript, SLC7A8, mapping to 14q11.2, within the lysinuric protein intolerance (LPI) critical region. This gene is highly expressed in skeletal muscle, intestine, kidney, and placenta and encodes a predicted protein of 535 amino acids, homologous to the amino acid permease CD98 light chain and cationic amino acid transporters. RNA in situ hybridization data on mouse embryos confirm the expression in kidney and intestine and, interestingly, reveal that SLC7A8 is also highly expressed in eye, in retinal pigmented epithelium, and in tooth buds at day 16.5 of gestation. Mutational analysis excluded any direct involvement of the SLC7A8 gene product in LPI disease. The homology data and the expression pattern are in agreement with the hypothesis that SLC7A8 represents a novel light chain interacting with the 4F2 heavy chain in the multimeric complex mediating neutral and/or cationic amino acid transport and cystine/glutamate exchange.

Geleophysic dysplasia: 7-year follow-up study of a patient with an intermediate form.

Geleophysic dysplasia (MIM *231050) is a rare autosomal recessive disorder, characterized by short stature with short limbs, brachydactyly, joint contractures, and a good-natured facial appearance. Infiltration of liver and cardiac leaflets has been reported in some patients. Based on the clinical picture and the detection of lysosome-like inclusions in hepatocytes, tracheal mucosa, chondrocytes, and skin fibroblasts, the underlying cause of the conditions is considered to be a generalized lysosomal storage defect. We report on a new case born to consanguineous parents, first observed at age 8 months, and for whom a 7-year follow-up is available.

Feasibility of prenatal diagnosis of lysinuric protein intolerance by linkage analysis: a case report.

Lysinuric protein intolerance (LPI) is a rare autosomal recessive defect of cationic amino acid transport (CAA), relatively common in Finland and Italy. After weaning, LPI patients present poor feeding, vomiting and failure to thrive. A severe pulmonary complication and episodes of metabolic imbalance may lead to death. Prenatal diagnosis has not been available due to lack of either biochemical or molecular markers to be used in the fetal period. The LPI locus has recently been assigned to chromosome 14q12, very close to the T-cell receptor alpha-chain (TCRA) locus. We carried out a prenatal diagnosis for LPI by linkage analysis in one LPI Italian family after CVS. For the haplotype analysis 11 DNA markers from the LPI critical region were used (D14S742, D14S50, D14S283, five TCRA intragenic polymorphic sites, D14S990, MYH7 and D14S80). It was concluded that the haplotype analysis indicated that the fetus was healthy as he had inherited the two wild alleles of the LPI locus. After birth, the clearances of CAA were measured and found to be in the normal range, thus confirming the result of the prenatal diagnosis. The prenatal diagnosis of LPI can now be offered to families affected by LPI.

Four novel mutations in the cystathionine beta-synthase gene: effect of a second linked mutation on the severity of the homocystinuric phenotype.

Homocystinuria due to cystathionine beta-synthase (CBS) deficiency is frequently caused by missense mutations. In this article, we report four novel missense mutations in the CBS gene: 172C-->T (R58W) linked in cis with A114V; 376A-->G (M126V); 904G-->A (E302K); and 1006C-->T (R336C). The CBS activity of the corresponding mutant enzymes expressed in Escherichia coli was greatly diminished, confirming the pathogenicity of these mutations. Western analysis showed that the R58W+A114V and M126V mutant enzymes were unstable in E. coli, while the E302K subunits were partially degraded to shorter products. Using site-directed mutagenesis we found that CBS containing either the R58W or A114V as the only mutations demonstrated 18% and 46% of normal activity, respectively. Both mutant forms of CBS were stable in E. coli. When these two mutations were expressed in cis, the resultant mutant protein exhibited activity 1.3% that of a control. All these in vitro results were in good agreement with the clinical manifestation in these patients. The Italian patient 2241, an A114V+R58W/M126V compound heterozygote, exhibited severe pyridoxine nonresponsive homocystinuria, while another Italian patient 2242, with an A114V/E302K genotype, responded to pyridoxine treatment and had a much milder phenotype. The third patient 3064, an English compound heterozygote for two severe mutations R336C and G307S, was B6 nonresponsive. This report of a ninth homocystinuric allele carrying two mutations in cis raises the possibility that double mutant alleles may be underestimated in homocystinuric patients. In this context, a search for additional mutations in cis may sometimes be necessary to establish a good genotype-phenotype relationship.

Mosaicism for the full mutation and a microdeletion involving the CGG repeat and flanking sequences in the FMR1 gene in eight fragile X patients.

The molecular mechanism of the fragile X syndrome is based on the expansion of an unstable CGG repeat in the 5' untranslated region of the FMR1 gene in most patients. This expansion is associated with an abnormal DNA methylation leading to the absence of production of FMR1 protein (FMRP). Such expansion apparently predisposes the repeat and flanking regions to further instability that may lead to mosaic conditions with a full mutation and a premutation or, rarely, with normal or reduced alleles that can sometimes be transcriptionally active. In this study we describe eight unrelated fragile X patients who are mosaic for both a full mutation and an allele of normal (four cases) or reduced size (four cases). Sequencing analysis of the deletion breakpoints in 6 patients demonstrated an internal deletion confined to the CGG repeat in four of them, which represents the most likely explanation for the regression of the full mutation to a normal sized allele. In two patients with a reduced allele, the deletion encompassed the entire CGG repeat and part of the flanking regions. Analysis of FMRP by Western blot was performed in one of the mosaics with a normal sized allele and in three of those with a reduced allele. In the first patient's lymphocytes FMRP was detected, whereas in the three other patients the deletion is likely to impair transcription as no FMRP was present in their lymphocytes.

Cystathionine beta-synthase mutations in homocystinuria.

The major cause of homocystinuria is mutation of the gene encoding the enzyme cystathionine beta-synthase (CBS). Deficiency of CBS activity results in elevated levels of homocysteine as well as methionine in plasma and urine and decreased levels of cystathionine and cysteine. Ninety-two different disease-associated mutations have been identified in the CBS gene in 310 examined homocystinuric alleles in more than a dozen laboratories around the world. Most of these mutations are missense, and the vast majority of these are private mutations. The two most frequently encountered of these mutations are the pyridoxine-responsive I278T and the pyridoxine-nonresponsive G307S. Mutations due to deaminations of methylcytosines represent 53% of all point substitutions in the coding region of the CBS gene.