De novo and inherited TCF20 pathogenic variants are associated with intellectual disability, dysmorphic features, hypotonia, and neurological impairments with similarities to Smith-Magenis syndrome

BACKGROUND

Neurodevelopmental disorders are genetically and phenotypically heterogeneous encompassing developmental delay (DD), intellectual disability (ID), autism spectrum disorders (ASDs), structural brain abnormalities, and neurological manifestations with variants in a large number of genes (hundreds) associated. To date, a few de novo mutations potentially disrupting TCF20 function in patients with ID, ASD, and hypotonia have been reported. TCF20 encodes a transcriptional co-regulator structurally related to RAI1, the dosage-sensitive gene responsible for Smith-Magenis syndrome (deletion/haploinsufficiency) and Potocki-Lupski syndrome (duplication/triplosensitivity).

METHODS

Genome-wide analyses by exome sequencing (ES) and chromosomal microarray analysis (CMA) identified individuals with heterozygous, likely damaging, loss-of-function alleles in TCF20. We implemented further molecular and clinical analyses to determine the inheritance of the pathogenic variant alleles and studied the spectrum of phenotypes.

RESULTS

We report 25 unique inactivating single nucleotide variants/indels (1 missense, 1 canonical splice-site variant, 18 frameshift, and 5 nonsense) and 4 deletions of TCF20. The pathogenic variants were detected in 32 patients and 4 affected parents from 31 unrelated families. Among cases with available parental samples, the variants were de novo in 20 instances and inherited from 4 symptomatic parents in 5, including in one set of monozygotic twins. Two pathogenic loss-of-function variants were recurrent in unrelated families. Patients presented with a phenotype characterized by developmental delay, intellectual disability, hypotonia, variable dysmorphic features, movement disorders, and sleep disturbances.

CONCLUSIONS

TCF20 pathogenic variants are associated with a novel syndrome manifesting clinical characteristics similar to those observed in Smith-Magenis syndrome. Together with previously described cases, the clinical entity of TCF20-associated neurodevelopmental disorders (TAND) emerges from a genotype-driven perspective.

A mutation in the nucleoporin-107 gene causes XX gonadal dysgenesis

Ovarian development and maintenance are poorly understood; however, diseases that affect these processes can offer insights into the underlying mechanisms. XX female gonadal dysgenesis (XX-GD) is a rare, genetically heterogeneous disorder that is characterized by underdeveloped, dysfunctional ovaries, with subsequent lack of spontaneous pubertal development, primary amenorrhea, uterine hypoplasia, and hypergonadotropic hypogonadism. Here, we report an extended consanguineous family of Palestinian origin, in which 4 females exhibited XX-GD. Using homozygosity mapping and whole-exome sequencing, we identified a recessive missense mutation in nucleoporin-107 (NUP107, c.1339G>A, p.D447N). This mutation segregated with the XX-GD phenotype and was not present in available databases or in 150 healthy ethnically matched controls. NUP107 is a component of the nuclear pore complex, and the NUP107-associated protein SEH1 is required for oogenesis in Drosophila. In Drosophila, Nup107 knockdown in somatic gonadal cells resulted in female sterility, whereas males were fully fertile. Transgenic rescue of Drosophila females bearing the Nup107D364N mutation, which corresponds to the human NUP107 (p.D447N), resulted in almost complete sterility, with a marked reduction in progeny, morphologically aberrant eggshells, and disintegrating egg chambers, indicating defective oogenesis. These results indicate a pivotal role for NUP107 in ovarian development and suggest that nucleoporin defects may play a role in milder and more common conditions such as premature ovarian failure.

Nonsyndromic Early-Onset Cone-Rod Dystrophy and Limb-Girdle Muscular Dystrophy in a Consanguineous Israeli Family are Caused by Two Independent yet Linked Mutations in ALMS1 and DYSF

Genetic analysis of clinical phenotypes in consanguineous families is complicated by coinheritance of large DNA regions carrying independent variants. Here, we characterized a family with early onset cone-rod dystrophy (CRD) and muscular dystrophy. Homozygosity mapping (HM) followed by whole exome sequencing revealed a nonsense mutation, p.R270*, in ALMS1 and two novel potentially disease-causing missense variants, p.R1581C and p.Y2070C, in DYSF. ALMS1 and DYSF are genetically and physically linked on chromosome 2 in a genomic region suggested by HM and associated with Alström syndrome, which includes CRD, and with limb girdle muscular dystrophy, respectively. Affected family members lack additional systemic manifestations of Alström syndrome but exhibit mild muscular dystrophy. RNA-seq data did not reveal any significant variations in ALMS1 transcripts in the human retina. Our study thus implicates ALMS1 as a nonsyndromic retinal disease gene and suggests a potential role of variants in interacting cilia genes in modifying clinical phenotypes.

An infant with a diagnostically challenging hepatic teratoma, hypofibrinogenemia, and adrenal neuroblastoma: case report

Teratomas of the liver are exceedingly rare. Neuroblastoma is the most common, extracranial solid tumor of infancy. We describe the case of a 2-month-old, female infant who presented with an abdominal mass arising in the right lobe of the liver, and a severe coagulopathy, which necessitated cryoprecipitate infusion. Biopsy was interpreted as hepatoblastoma. Following resection, difficulty classifying the mass led to several consultations, and an eventual diagnosis of teratoma. During follow-up, the patient was diagnosed with right adrenal neuroblastoma, which, in retrospect, had been present before the hepatic resection. To our knowledge, these 2 tumors have never been reported together, or in combination with isolated hypofibrinogenemia.

Mutant cohesin in premature ovarian failure

Premature ovarian failure is a major cause of female infertility. The genetic causes of this disorder remain unknown in most patients. Using whole-exome sequence analysis of a large consanguineous family with inherited premature ovarian failure, we identified a homozygous 1-bp deletion inducing a frameshift mutation in STAG3 on chromosome 7. STAG3 encodes a meiosis-specific subunit of the cohesin ring, which ensures correct sister chromatid cohesion. Female mice devoid of Stag3 are sterile, and their fetal oocytes are arrested at early prophase I, leading to oocyte depletion at 1 week of age.

Mutations in FKBP10, which result in Bruck syndrome and recessive forms of osteogenesis imperfecta, inhibit the hydroxylation of telopeptide lysines in bone collagen

Although biallelic mutations in non-collagen genes account for <10% of individuals with osteogenesis imperfecta, the characterization of these genes has identified new pathways and potential interventions that could benefit even those with mutations in type I collagen genes. We identified mutations in FKBP10, which encodes the 65 kDa prolyl cis-trans isomerase, FKBP65, in 38 members of 21 families with OI. These include 10 families from the Samoan Islands who share a founder mutation. Of the mutations, three are missense; the remainder either introduce premature termination codons or create frameshifts both of which result in mRNA instability. In four families missense mutations result in loss of most of the protein. The clinical effects of these mutations are short stature, a high incidence of joint contractures at birth and progressive scoliosis and fractures, but there is remarkable variability in phenotype even within families. The loss of the activity of FKBP65 has several effects: type I procollagen secretion is slightly delayed, the stabilization of the intact trimer is incomplete and there is diminished hydroxylation of the telopeptide lysyl residues involved in intermolecular cross-link formation in bone. The phenotype overlaps with that seen with mutations in PLOD2 (Bruck syndrome II), which encodes LH2, the enzyme that hydroxylates the telopeptide lysyl residues. These findings define a set of genes, FKBP10, PLOD2 and SERPINH1, that act during procollagen maturation to contribute to molecular stability and post-translational modification of type I procollagen, without which bone mass and quality are abnormal and fractures and contractures result.

Genome-wide linkage in a highly consanguineous pedigree reveals two novel loci on chromosome 7 for non-syndromic familial Premature Ovarian Failure

Background

The human condition known as Premature Ovarian Failure (POF) is characterized by loss of ovarian function before the age of 40. A majority of POF cases are sporadic, but 10–15% are familial, suggesting a genetic origin of the disease. Although several causal mutations have been identified, the etiology of POF is still unknown for about 90% of the patients.

Methodology/Principal Findings

We report a genome-wide linkage and homozygosity analysis in one large consanguineous Middle-Eastern POF-affected family presenting an autosomal recessive pattern of inheritance. We identified two regions with a LOD_max of 3.26 on chromosome 7p21.1-15.3 and 7q21.3-22.2, which are supported as candidate regions by homozygosity mapping. Sequencing of the coding exons and known regulatory sequences of three candidate genes (DLX5, DLX6 and DSS1) included within the largest region did not reveal any causal mutations.

Conclusions/Significance

We detect two novel POF-associated loci on human chromosome 7, opening the way to the identification of new genes involved in the control of ovarian development and function.

Novel mutations of MYO7A and USH1G in Israeli Arab families with Usher syndrome type 1

PURPOSE

This study investigated the genetic basis for Usher syndrome type 1 (USH1) in four consanguineous Israeli Arab families.

METHODS

Haplotype analysis for all known USH1 loci was performed in each family. In families for which haplotype analysis was inconclusive, we performed genome-wide homozygosity mapping using a single nucleotide polymorphism (SNP) array. For mutation analysis, specific primers were used to PCR amplify the coding exons of the MYO7A, USH1C, and USH1G genes including intron-exon boundaries. Mutation screening was performed with direct sequencing.

RESULTS

A combination of haplotype analysis and genome-wide homozygosity mapping indicated linkage to the USH1B locus in two families, USH1C in one family and USH1G in another family. Sequence analysis of the relevant genes (MYO7A, USH1C, and USH1G) led to the identification of pathogenic mutations in all families. Two of the identified mutations are novel (c.1135-1147dup in MYO7A and c.206-207insC in USH1G).

CONCLUSIONS

USH1 is a genetically heterogenous condition. Of the five USH1 genes identified to date, USH1C and USH1G are the rarest contributors to USH1 etiology worldwide. It is therefore interesting that two of the four Israeli Arab families reported here have mutations in these two genes. This finding further demonstrates the unique genetic structure of the Israeli population in general, and the Israeli Arab population in particular, which due to high rates of consanguinity segregates many rare autosomal recessive genetic conditions.

Early prenatal ventriculomegaly due to an AIFM1 mutation identified by linkage analysis and whole exome sequencing

The identification of disease causing mutation in patients with neurodegenerative disorders originating from small, non-consanguineous families is challenging. Three siblings were found to have ventriculomegaly at early gestation; postnatally, there was no acquisition of developmental milestones, and the muscles of the children were dystrophic. Plasma and CSF lactate levels were normal, but the activities of mitochondrial complex I and IV were markedly decreased. Using linkage analysis in the family, followed by whole exome sequencing of a single patient, we identified a pathogenic mutation in the AIFM1 gene which segregated with the disease state and was absent in 86 anonymous controls. This is the second report of a mutation in the AIFM1 gene, extending the clinical spectrum to include prenatal ventriculomegaly and underscores the importance of AIF for complex I assembly. In summary, linkage analysis followed by exome sequencing of a single patient is a cost-effective approach for the identification of disease causing mutations in small non-consanguineous families.

Genomic duplication and overexpression of TJP2/ZO-2 leads to altered expression of apoptosis genes in progressive nonsyndromic hearing loss DFNA51

Age-related hearing loss is due to death over time, primarily by apoptosis, of hair cells in the inner ear. Studies of mutant genes responsible for inherited progressive hearing loss have suggested possible mechanisms for hair cell death, but critical connections between these mutations and the causes of progressive hearing loss have been elusive. In an Israeli kindred, dominant, adult-onset, progressive nonsyndromic hearing loss DFNA51 is due to a tandem inverted genomic duplication of 270 kb that includes the entire wild-type gene encoding the tight junction protein TJP2 (ZO-2). In the mammalian inner ear, TJP2 is expressed mainly in tight junctions, and also in the cytoplasm and nuclei. TJP2 expression normally decreases with age from embryonic development to adulthood. In cells of affected family members, TJP2 transcript and protein are overexpressed, leading to decreased phosphorylation of GSK-3beta and to altered expression of genes that regulate apoptosis. These results suggest that TJP2- and GSK-3beta-mediated increased susceptibility to apoptosis of cells of the inner ear is the mechanism for adult-onset hearing loss in this kindred and may serve as one model for age-related hearing loss in the general population.

Disruption of the podosome adaptor protein TKS4 (SH3PXD2B) causes the skeletal dysplasia, eye, and cardiac abnormalities of Frank-Ter Haar Syndrome

Frank-Ter Haar syndrome (FTHS), also known as Ter Haar syndrome, is an autosomal-recessive disorder characterized by skeletal, cardiovascular, and eye abnormalities, such as increased intraocular pressure, prominent eyes, and hypertelorism. We have conducted homozygosity mapping on patients representing 12 FTHS families. A locus on chromosome 5q35.1 was identified for which patients from nine families shared homozygosity. For one family, a homozygous deletion mapped exactly to the smallest region of overlapping homozygosity, which contains a single gene, SH3PXD2B. This gene encodes the TKS4 protein, a phox homology (PX) and Src homology 3 (SH3) domain-containing adaptor protein and Src substrate. This protein was recently shown to be involved in the formation of actin-rich membrane protrusions called podosomes or invadopodia, which coordinate pericellular proteolysis with cell migration. Mice lacking Tks4 also showed pronounced skeletal, eye, and cardiac abnormalities and phenocopied the majority of the defects associated with FTHS. These findings establish a role for TKS4 in FTHS and embryonic development. Mutation analysis revealed five different homozygous mutations in SH3PXD2B in seven FTHS families. No SH3PXD2B mutations were detected in six other FTHS families, demonstrating the genetic heterogeneity of this condition. Interestingly however, dermal fibroblasts from one of the individuals without an SH3PXD2B mutation nevertheless expressed lower levels of the TKS4 protein, suggesting a common mechanism underlying disease causation.

Misleading findings of homozygosity mapping resulting from three novel mutations in NPHS1 encoding nephrin in a highly inbred community

PURPOSE

Congenital nephrotic syndrome of the Finnish type (CNF, NPHS1) is a rare autosomal recessive disease caused by mutations in the NPHS1 gene encoding nephrin. We diagnosed congenital nephrotic syndrome in 12 children living in a village near Jerusalem. Most of the inhabitants are descendants of one Muslim family and have maintained their isolation by preference of consanguineous marriages. The aim of this study was to confirm that the NPHS1 gene is responsible for congenital nephrotic syndrome in our population, applying homozygosity mapping.

METHODS

DNA samples were genotyped by four microsatellite markers that were in linkage disequilibrium with the NPHS1 gene on chromosome 19q13.1. Immunoperoxidase staining was used to study the expression of nephrin, and mutations were subsequently identified by direct sequencing of the entire coding region of the NPHS1 gene.

RESULTS

Haplotype analysis revealed several different haplotypes, leading us to assume erroneously that there was genetic heterogeneity of congenital nephrotic syndrome. Because nephrin was completely absent in kidney tissue of one patient, direct sequencing of all DNA samples was performed, yielding three novel mutations: c.1138C>T (p.Gln380X), c.2160_ 2161insC (p.Cys721fs), and c.1707C>G (p.Ser569Arg). Patients were either homozygous for one of these mutations or compound heterozygotes, and they differed in their phenotype.

CONCLUSION

We report the potential pitfalls of performing homozygosity mapping in a highly consanguineous population and discuss the phenomenon of multiple mutations in a given gene within an isolate.

Glutaric aciduria type 1: clinical, biochemical and molecular findings in patients from Israel

Glutaric aciduria type 1 (GA1) is a rare cerebral organic aciduria which typically manifests as an acute encephalopathic crisis followed by profound long-term neurological handicap. We report the diagnosis of 12 new patients from a single laboratory in Israel during a 5-year period. Eleven of the 12 were of Palestinian origin, and only two were related. One patient was asymptomatic whilst one was mildly, one moderately and nine severely affected, two of whom had unusual MRI findings. Two patients had normal glutaric acid excretion and normal blood glutarylcarnitine levels yet glutarylcarnitine excretion was increased, indicating its utility as a diagnostic marker. Four novel GCDH mutations (Thr193_Arg194insHis, Asn329Ser, Thr341Pro, Met405Val) and five previously reported mutations (Ser119Leu, Leu283Pro, Ala293Thr, Gly390Arg and Thr416Ile) were identified. Severely and mildly affected or even asymptomatic patients shared the same genotypes (Thr416Ile/Thre416Ile and Aal293Thr/Thr193_Arg194insHis). Knowledge of the responsible mutation enabled successful prenatal diagnosis on chorionic villous DNA in three families. In conclusion, GA1 is genetically heterogeneous and has a relatively high incidence in the Palestinian population, reflecting the historical tradition of marriages within extended kindreds, particularly in isolated villages. Additional genetic and/or environmental factors must account for the phenotypic heterogeneity in patients with the same genotype. The diagnosis was not suspected in the majority of cases despite typical clinical and/or neuroimaging features, suggesting that glutaric aciduria may be under-diagnosed. Greater awareness of glutaric aciduria amongst pediatricians, neonatologists and radiologists is the key to identifying the disorder in the presymptomatic phase and preventing its catastrophic consequences.

OEIS complex: prenatal ultrasound and autopsy findings

OBJECTIVE

To describe prenatal ultrasound and autopsy findings in fetuses with OEIS (omphalocele, bladder exstrophy, imperforate anus, spina bifida) complex.

METHODS

This was a retrospective study of the nine cases with OEIS complex diagnosed at our center using detailed fetal ultrasound during the last 10 years. We summarized the fetal ultrasound findings that led to the diagnosis and compared them with the autopsy results.

RESULTS

All affected fetuses were diagnosed using detailed fetal ultrasound after 16 weeks' gestation. The main prenatal findings were omphalocele, skin-covered lumbosacral neural tube defect, non-visualized bladder and limb defects. Prenatal sonography failed to detect the abnormal genitalia, bladder exstrophy and anal atresia. All cases had abnormalities in a 'diaper distribution', which helped in making the prenatal diagnosis. Eight of the nine couples chose to terminate the pregnancies following multidisciplinary counseling. The pregnancy that was continued was a case with dizygotic twins discordant for OEIS, and the affected fetus died in utero.

CONCLUSIONS

The combination of the following ultrasound findings: ventral wall defect, spinal defect and a non-visualized bladder with or without limb defects, are characteristic of OEIS complex. Diagnosis can be made with confidence as early as 16 weeks' gestation, although earlier diagnosis may be possible.

Molecular, biochemical, and genetic characterization of a female patient with Lesch-Nyhan disease

Lesch-Nyhan disease (LND) is a rare X-linked recessive disorder caused by virtually complete deficiency of activity of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT; EC 2.4.2.8). Human HPRT is encoded by a single structural gene located on the long arm of the X-chromosome (Xq26). The classical LND phenotype occurs almost exclusively in males, manifested in excessive purine production and characteristic neurological manifestations, including compulsive self-mutilation, choreoathetosis, spasticity, and occasionally developmental delay. Heterozygous females are usually phenotypically normal, due to the random inactivation of the X chromosome (Lyonization mechanism). However, six females were reported to be affected with the full biochemical and clinical manifestations of LND. All these cases were heterozygous for an HPRT mutation. Absence of transcription of the normal HPRT allele was attributed in all of them to non-random inactivation of the X chromosome carrying the normal allele. Here we describe an additional LND female, who presented with acute renal failure at the age of two months, in whom absence of transcription of the two HPRT alleles occurred due to as yet undescribed mechanism in LND females: the transcription of one HPRT allele was blocked due to a de novo X chromosome-autosome translocation 46,XX,t(X:2)(q26:p25), with a breaking point encompassing the HPRT gene locus, whereas the transcription of the normal allele was inhibited due to non-random inactivation of the second X-chromosome. Cultured fibroblasts from this patient exhibited the biochemical alterations in purine nucleotide metabolism characteristic of male LND fibroblasts.

Chromosome aberration and environmental physical activity: Down syndrome and solar and cosmic ray activity, Israel, 1990-2000

The possibility that environmental effects are associated with chromosome aberrations and various congenital pathologies has been discussed previously. Recent advances in the collection and computerization of data make studying these potential associations more feasible. The aim of this study was to investigate a possible link between the number of Down syndrome (DS) cases detected prenatally or at birth yearly in Israel over a 10-year period compared with the levels of solar and cosmic ray activity 1 year before the detection or birth of each affected child. Information about 1,108,449 births was collected for the years 1990-2000, excluding 1991, when data were unavailable. A total of 1,310 cases of DS were detected prenatally or at birth--138 in the non-Jewish community and 1,172 in the Jewish population. Solar activity indices--sunspot number and solar radio flux 2,800 MHz at 10.7 cm wavelength for 1989-1999--were compared with the number of DS cases detected. Pearson correlation coefficients (r) and their probabilities (P) were established for the percentage of DS cases in the whole population. There was a significant inverse correlation between the indices of solar activity and the number of cases of DS detected--r=-0.78, P=0.008 for sunspot number and r=-0.76, P=0.01 for solar flux. The possibility that cosmophysical factors inversely related to solar activity play a role in the pathogenesis of chromosome aberrations should be considered. We have confirmed a strong trend towards an association between the cosmic ray activity level and the incidence of DS.

A single nucleotide substitution that abolishes the initiator methionine codon of the GLDC gene is prevalent among patients with glycine encephalopathy in Jerusalem

Glycine encephalopathy (GE) (non-ketotic hyperglycinemia) is an autosomal recessive neurometabolic disease caused by defective activity of the glycine cleavage system. Clinically, patients present usually in the neonatal period with hypotonia, encephalopathy, hiccups and breath arrests with or without overt seizures. GE is considered rare, but its incidence is relatively high in several geographical areas around the world. We report a novel mutation causing GE in six extended Arab families, all from a small suburban village (population 5,000). A methionine to threonine change in the initiation codon of the glycine decarboxylase gene led to markedly reduced glycine decarboxylase mRNA levels and abolished glycine cleavage system activity.

Impaired mitochondrial glutamate transport in autosomal recessive neonatal myoclonic epilepsy

Severe neonatal epilepsies with suppression-burst pattern are epileptic syndromes with either neonatal onset or onset during the first months of life. These disorders are characterized by a typical electroencephalogram pattern--namely, suppression burst, in which higher-voltage bursts of slow waves mixed with multifocal spikes alternate with isoelectric suppression phases. Here, we report the genetic mapping of an autosomal recessive form of this condition to chromosome 11p15.5 and the identification of a missense mutation (p.Pro206Leu) in the gene encoding one of the two mitochondrial glutamate/H(+) symporters (SLC25A22, also known as "GC1"). The mutation cosegregated with the disease and altered a highly conserved amino acid. Functional analyses showed that glutamate oxidation in cultured skin fibroblasts from patients was strongly defective. Further studies in reconstituted proteoliposomes showed defective [(14)C]glutamate uniport and [(14)C]glutamate/glutamate exchange by mutant protein. Moreover, expression studies showed that, during human development, SLC25A22 is specifically expressed in the brain, within territories proposed to contribute to the genesis and control of myoclonic seizures. These findings provide the first direct molecular link between glutamate mitochondrial metabolism and myoclonic epilepsy and suggest potential insights into the pathophysiological bases of severe neonatal epilepsies with suppression-burst pattern.

Prenatal diagnosis for arginase deficiency by second-trimester fetal erythrocyte arginase assay and first-trimesterARG1 mutation analysis

Hyperargininemia is a progressive neurometabolic disorder caused by deficiency of hepatic cytosolic arginase I, resulting from mutations in the ARG1 gene. We diagnosed arginase deficiency in a three-year-old male child of first-cousin Palestinian Arab parents. Prenatal diagnosis of an unaffected fetus was achieved in the second trimester of a subsequent pregnancy by cordocentesis and analysis of arginase activity in fetal erythrocytes. ARG1 mutation analysis in the proband revealed homozygosity for a deletion of 10,753 bp extending from the first intron to beyond the poly (A) site of the gene. This is the first gross deletion in the ARG1 gene to be identified and the first mutation to be described in an arginase-deficient patient of this ethnic origin. The identification of the ARG1 deletion in this family enabled first-trimester prenatal diagnosis in a subsequent pregnancy by multiplex PCR analysis performed on chorionic villous DNA.

A patient with Prader-Willi syndrome and a supernumerary marker chromosome r(15)(q11.1-13p11.1)pat and maternal heterodisomy

We report on a Prader-Willi patient with a de novo supernumerary marker chromosome (SMC) in 16% of the cells. The SMC was a ring chromosome and it included the PWS/AS critical region as was demonstrated by FISH. Segregation analysis indicated that the SMC originated from a paternal chromosome 15 and the two normal chromosomes 15 of the patients were of the maternal homologues. Namely, the patient had maternal heterodisomy in 85% of the cells and triplication of the PWS/AS region in 15% of the cells. The Prader-Willi features were the result of the low mosaicism of the SMC. The evolution of the maternal heterodisomy and the SMC were two unrelated events, the occurrence of both events in the same embryo rescued it from lethality.

Prenatal diagnosis of Down syndrome: ten year experience in the Israeli population

Second trimester maternal serum biochemical markers, introduced between 1990 and 1995, were supplemented with new ultrasound methods at 14-16 weeks and first trimester biochemical markers between 1995 and 2000. This study evaluated the effectiveness of a Down syndrome (DS) prevention program among the Israeli Jewish population between 1990 and 2000. We collected data on the total number of prenatal tests performed on Israeli Jewish women, DS cases detected prenatally and DS livebirths in Israel during these years. We also studied the use of the newer screening tests in 1990, 1992, and 2000. Between 1990 and 1995, use of chromosomal studies for DS in this population increased from 11.3% to 21.6% and the percentage of cases detected prenatally from 53% to 70%. However, between 1996 and 2000, even with the new screening methods, the utilization rate remained similar (20.7% and 19.8%, respectively) and the percentage detected prenatally decreased to 61% in 2000. The total cost per case detected increased from $47,971 US dollars in 1990 to $75,229 US dollars in 1992, and to $190,171 US dollars in 2000. Between 1990 and 1995, improvement in the percentage of cases detected prenatally was associated with a significant increase in the amniocentesis rate-both are attributed to the introduction of second trimester maternal serum biochemical marker tests. Unexpectedly, the introduction between 1995 and 2000 of new genetic methods to assess the DS risk did not improve the percentage detected or reduce the amniocentesis rate, and was accompanied by an increased cost per case detected.

Increased risk for developmental delay in Saethre-Chotzen syndrome is associated with TWIST deletions: an improved strategy for TWIST mutation screening

The majority of patients with Saethre-Chotzen syndrome have mutations in the TWIST gene, which codes for a basic helix-loop-helix transcription factor. Of the genetic alterations identified in TWIST, nonsense mutations, frameshifts secondary to small deletions or insertions, and large deletions implicate haploinsufficiency as the pathogenic mechanism. We identified three novel intragenic mutations and six deletions in our patients by using a new strategy to screen for TWIST mutations. We used polymerase chain reaction (PCR) amplification with subsequent sequencing to identify point mutations and small insertions or deletions in the coding region, and real-time PCR-based gene dosage analysis to identify large deletions encompassing the gene, with confirmation by microsatellite and fluorescence in situ hybridization (FISH) analyses. The size of the deletions can also be analyzed by using the gene dosage assay with "PCR walking" across the critical region. In 55 patients with features of Saethre-Chotzen syndrome, 11% were detected to have deletions by real-time gene dosage analysis. Two patients had a translocation or inversion at least 260 kb 3' of the gene, suggesting they had position-effect mutations. Of the 37 patients with classic features of Saethre-Chotzen syndrome, the overall detection rate for TWIST mutations was 68%. The risk for developmental delay in patients with deletions involving the TWIST gene is approximately 90% or eight times more common than in patients with intragenic mutations.

Uniparental disomy in fetuses diagnosed with balanced Robertsonian translocations: risk estimate

Forty-two fetuses with non-homologous Robertsonian translocations were analyzed for uniparental disomy (UPD). One fetus with a de novo translocation t(13q;14q) had maternal isodisomy of chromosome 14. In a summary of the published data (including the present study), 315 cases were analyzed for UPD after prenatal diagnosis of balanced Robertsonian translocations, of these two fetuses had UPD, giving a risk estimate of 0.65% (CI 0.2-2.3). This risk justifies the recommendation of UPD analysis in fetuses diagnosed prenatally with Robertsonian translocations, with the emphasis on the chromosomes known to contain imprinted genes, such as 14 and 15. We also discuss the possibility of UPD in offspring of Robertsonian translocation carriers with normal karyotype. Based on the risk for UPD in fetuses with Robertsonian translocation we suggest to test these fetuses for UPD and to do so on amniocytes rather than chorionic villi when the risk for unbalanced karyotype is approximately 1%, comparable to the risk for UPD.

A deletion mutation in GJB6 cooperating with a GJB2 mutation in trans in non-syndromic deafness: A novel founder mutation in Ashkenazi Jews

A deletion of at least 140 kb starting approximately 35kb upstream (telomeric) to the GJB2 (CX26) gene was identified in 7 patients from 4 unrelated Jewish Ashkenazi families with non-syndromic hearing loss. These patients were heterozygous for one of the common mutations 167delT or 35delG in the GJB2 gene in trans to the deletion. The deletion started at 5' side of the GJB6 (CX30) gene including the first exon and it did not affect the integrity of the GJB2 gene. The deletion mutation segregated together with the hearing loss, and was not found in a control group of 100 Ashkenazi individuals. We suggest that the deletion is a recessive mutation causing hearing loss in individuals that are double heterozygous for the deletion and for a mutation in the GJB2 gene. The effect of the deletion mutation could be due to a digenic mode of inheritance of GJB2 and GJB6 genes that encode two different connexins; connexin 26 and connexin 30, or it may abolish control elements that are important in the expression of the GJB2 gene in the cochlea. Regardless which of the options is valid, it is apparent that the deletion mutation provides a new insight into connexin function in the auditory system. The deletion mutation was on the same haplotypic background in all the families, and therefore is a founder mutation that increases the impact of GJB2 in the etiology of prelingual recessive non-syndromic hearing loss in the Ashkenazi population.

Clinical-biochemical correlation in molecularly characterized patients with Niemann-Pick type C

PURPOSE

Niemann-Pick disease type C (NP-C) is an autosomal recessive lipid storage disease manifested by an impairment in cellular cholesterol homeostasis. The clinical phenotype of NP-C is extremely variable, ranging from an acute neonatal form to an adult late-onset presentation. To facilitate phenotype-genotype studies, we have analyzed multiple Israeli NP-C families.

METHODS

The severity of the disease was assessed by the age at onset, hepatic involvement, neurological deterioration, and cholesterol esterification studies. Screening of the entire NPC1 coding sequence allowed for molecular characterization and identification of disease causing mutations.

RESULTS

A total of nine NP-C index cases with mainly neurovisceral involvement were characterized. We demonstrated a possible link between the severity of the clinical phenotype and the cholesterol esterification levels in fibroblast cultures following 24 hours of in vitro cholesterol loading. In addition, we identified eight novel mutations in the NPC1 gene.

CONCLUSIONS

Our results further support the clinical and allelic heterogeneity of NP-C and point to possible association between the clinical and the biochemical phenotype in distinct affected Israeli families.

Variables influencing parental perception of inherited metabolic diseases before and after genetic counselling

The present study was undertaken to characterize the variables that influence parental perception of metabolic disorders and their genetic origin before and after genetic counselling, the effect of counselling on parental attitudes towards prenatal diagnosis and pregnancy termination, and the factors affecting parental coping with burden. Parents of children with metabolic diseases from 32 Arab-Muslim families were interviewed, answering a pre-structured questionnaire. These interviews indicate the following. (1) Traditional belief and religious commitment are more important determinants than education in parental perception of inherited metabolic diseases. (2) The number of affected children has a greater impact on parental evaluation of the burden than the number of healthy children. The social component, i.e. the way families are viewed by society, is the most significant factor of the burden. (3) Parents use different techniques to divide responsibility regarding reproduction. Having a healthy child and the availability of prenatal diagnosis and pregnancy termination were the two most important factors in parental reproductive decision making. In the absence of a healthy child and when the burden was perceived as too heavy, parents tended 'not to decide'. (4) Parental attitude to pregnancy termination was dependent on two factors: religious commitment (leading to objection) and severity of disease (leading to flexibility and approval). (5) In almost all families, genetic counselling altered parental perception of the disease and its hereditary origin. We conclude that genetic counselling and population education may be helpful in the prevention of consanguineous marriages and in family planning, even in a society that values traditional beliefs very highly.

Aspartylglucosaminuria among Palestinian Arabs

Aspartylglucosaminuria (AGU) is a rare disorder of glycoprotein metabolism caused by the deficiency of the lysosomal enzyme aspartylglucosaminidase (AGA). AGU is inherited as an autosomal recessive trait and occurs with a high frequency in Finland because of a founder effect. While very few patients with AGU have been reported from non-Finnish origin, we diagnosed the disorder in 8 patients originating from 3 unrelated families, all Palestinian Arabs from the region of Jerusalem. The clinical diagnosis of AGU is often difficult, in particular early in the course of the disease, and most of the patients are diagnosed after the age of 5 years. However, since these patients excrete early large amounts of aspartylglucosamine in urine, biochemical screening is easy by urine chromatography.

A syndrome including thumb malformations, microcephaly, short stature, and hypogonadism

We report on eight patients from seven different families affected with a syndrome which includes thumb defects, short stature, microcephaly, and mental retardation. Most of the patients had additional malformations, in particular amenorrhoea and azoospermia in the adults. There were no haematological manifestations and the chromosomes were normal without evidence of breakage even after stimulation. In five of the cases the probands' mother received hormonal treatment before or at the beginning of her pregnancy or both. The syndrome may be inherited as an autosomal recessive trait since the patients included both males and females and their parents were related in most cases. In addition, supporting this possibility, they all originated from a small village which may be considered as an isolate. However, in all cases but one, only one person was affected in each family and there was a significant apparent excess of healthy sibs of the probands. These observations may be the result of the variability of the syndrome or a more complex type of inheritance.

Trisomy 2: confined placental mosaicism in a fetus with intrauterine growth retardation

In a pregnancy that was monitored due to increased risk for Down syndrome in the triple test, a normal karyotype was found in amniocentesis. Follow-up by serial ultrasound examinations revealed intrauterine growth retardation (IUGR) at 20 weeks of gestation. The parents decided to terminate the pregnancy and the karyotype of the placental fibroblasts was 47,XX,+2. Analysis of polymorphic markers of chromosome 2 demonstrated (a) that trisomy 2 was confined to the placenta (CPM), (b) that the trisomy 2 cell line was a result of a meiotic I error of paternal origin, and (c) that the fetal tissues with a normal karyotype were biparental disomy 2.

Renal anomalies in Marden-Walker syndrome: a clue for prenatal diagnosis

Marden-Walker syndrome is an autosomal-recessive disorder characterized by psychomotor retardation, blepharophimosis, joint contractures, arachnodactyly, failure to thrive, and, infrequently, renal anomalies. We report on the prenatal diagnosis of Marden-Walker syndrome in a fetus which had had a previously affected sib with this syndrome. The ultrasonic findings indicative of the diagnosis in this fetus were intrauterine growth retardation and renal cystic disease. We emphasize the importance of renal anomalies which, when present in combination with other ultrasound evidence of this syndrome, should be used as a clue for the diagnosis of Marden-Walker syndrome.

The regulatory role of tri-iodothyronine on the production of alpha-fetoprotein and albumin by mouse fetal liver cells

The purpose of this study was to assess possible effects of tri-iodothyronine (T3) on the production of alpha fetoprotein (AFP) and albumin by mouse fetal liver cells. AFP from serum-free conditioned media of TIB73 mouse fetal liver cells was measured by immunoradiometric assay and albumin was measured by chromogenic assay. The expression of mRNAs was quantified by Northern blotting analysis. A marked inhibition of AFP secretion was found as well as an increase in albumin produced by T3 in a dose-dependent manner. The effects of T3 AFP and albumin secretion paralleled the effects of T3 on the steady-state expression of mRNAs encoding albumin and AFP. These data may point to a possible role of T3 in the transcriptional switch from AFP to albumin during fetal development and may explain the observation of high levels of AFP in cases of congenital hypothyroidism.

Survival in an infant with a prenatally diagnosed Meckel syndrome variant

An infant with occipital encephalocele and unilateral multicystic kidney, diagnosed prenatally, was considered to have a variant of the Meckel syndrome (MS). This case is exceptional in that the infant was alive and healthy following surgical repair of the encephalocele, with normal function of the unaffected kidney, at age 5 months. Based on this experience, in fetuses or infants with MS, thorough evaluation of both kidneys is imperative prior to suggesting either termination of pregnancy, or withholding of life-sustaining medical treatment in infants already delivered.

Direct measurements of the dextran-dependent calcium uptake by rat peritoneal mast cells

The metallochromic indicator murexide has been used to monitor calcium concentration changes during the dextran-induced, phosphatidylserine-dependent degranulation of rat peritoneal mast cells. The dextran-induced Ca2+-uptake showed an absolute dependence on the presence of phosphatidylserine. The extent of Ca2+-uptake increased with phosphatidylserine in a concentration-dependent manner. At 25 degrees C the half-life of the uptake process equalled 35 +/- 5 s. Exposure of the mast cells to dextran in the presence of Ca2+, but in the absence of phosphatidylserine, desensitized the cells. The subsequent addition of phosphatidylserine failed to restore the Ca2+-uptake activity. However, the Ca2+-ionophore A23187 did promote Ca2+ uptake by the cells without PS.

Structure-activity relationship in the mast cell degranulating capacity of neurotensin fragments

The mast cell degranulating capacity of neurotensin and three of its fragments was examined. In Tyrode solution (137 mM NaCl, 2.7 mM KCl, 0.4 mM NaH2PO4, 1.4 mM CaCl2, 1 mM MgCl2, 10 mM Hepes, 5.6 mM glucose, pH 7.4), neither intact neurotensin nor its C-terminal tripeptide (Tyr-Ile-Leu) caused any release of histamine. Concentrations of neurotensin exceeding 10(-4)M did cause histamine release but through lysis of the cells. The C-terminal hexa- and octapeptides of neurotensin (Arg-Arg-Pro-Tyr-Ile-Leu and Lys-Pro-Arg-Arg-Pro-Tyr-Ile-Leu, respectively) induced a non-cytolytic release of histamine with the latter peptide being more active (ED50 = 90 microM for the hexapeptide and 13 microM for the octapeptide). This release was not affected by the C-terminal tripeptide. It was found to be calcium-dependent and was inhibited by the anti-allergic drug, disodium cromoglycate. Phosphatidylserine did not enhance release of histamine and saturation of the immunoglobulin E (IgE) receptors did not inhibit it.