Combining fetal sonography with genetic and allele pathogenicity studies to secure a neonatal diagnosis of Bardet-Biedl syndrome.

Bardet-Biedl syndrome (BBS) is a rare pediatric ciliopathy characterized by marked clinical variability and extensive genetic heterogeneity. Typical diagnosis of BBS is secured at a median of 9 years of age, and sometimes well into adolescence. Here, we report a patient in whom prenatal detection of increased nuchal fold, enlarged echogenic kidneys, and polydactyly prompted us to screen the most commonly mutated genes in BBS and the phenotypically and genetically overlapping ciliopathy, Meckel-Gruber syndrome (MKS). We identified the common Met390Arg mutation in BBS1 in compound heterozygosity with a novel intronic variant of unknown significance (VUS). Testing of mRNA harvested from primary foreskin fibroblasts obtained shortly after birth revealed the VUS to induce a cryptic splice site, which in turn led to a premature termination and mRNA degradation. To our knowledge, this is the earliest diagnosis of BBS in the absence of other affected individuals in the family, and exemplifies how combining clinical assessment with genetic and timely assays of variant pathogenicity can inform clinical diagnosis and assist with patient management in the prenatal and neonatal setting.

Partial trisomy 10p12.33 and partial monosomy 13q32.1: case report and a literature review.

We report on a preterm neonate with a deletion of the distal long arm of chromosome 13q32.1 and partial trisomy of the short arm of chromosome 10p12.33. The patient has intrauterine growth retardation, microphthalmia, macrocephaly, holoprosencephaly, patent ductus arteriosus, aortic isthmus hypoplasia, right renal agenesis, imperforate anus, ambiguous genitalia, pleural effusion and vertebral anomaly. Analysis using an oligonucleotide microarray (U-array Cyto6000 array platform (Human Genome build: hg 18) indicated that there was a partial trisomy of chromosome 10(19.5 Mb gain) involving 298 oligonucleotides from 10pter to 10p12.33, and a partial monosomy of chromosome 13(18.3 Mb deleted) involving 313 oligonucleotides from 13q32.1 to 13qter. This is the first report of a patient with partial trisomy 10p12.33 and partial monosomy 13q32.1.

Specific substrate for CLN2 protease/tripeptidyl-peptidase I assay.

The classic late infantile neuronal ceroid lipofuscinosis (LINCL, CLN2) is a fatal neurodegenerative disorder that results from mutations in a gene encoding a lysosomal proteinase, known as CLN2 protease (CLN2p) or tripeptidyl peptidase I (TPP-I). Three different substrates, fluorescein isothiocyanate-labelled haemoglobin, A-F-F-7-amino-4-methylcoumarin (AAF-AMC) and G-F-F-L-7-amino-4-trifluoromethylcoumarin (GFFL-AFC) have been used for the CLN2p/TPP-I assay with varying degrees of residual activities in patients with LINCL. Further, conclusive identification of carriers are not possible with the first two substrates. An assay for the CLN2p/TPP-I based on the cleavage of amino terminal tripeptide from G-F-F-L-AFC was applied to prenatal and postnatal diagnosis of LINCL patients and heterozygote carriers. In leukocytes, the CLN2p/TPP-I activities in controls and heterozygote carriers were 1995 +/- 154 (n = 15) and 918 +/- 253 (n = 15) nmol/h/mg protein respectively. No CLN2p/TPP-I activity was detectable in all but two patients. These two patients had less than 2% residual activity, and had delayed clinical symptoms for LINCL. This shows that the G-F-F-L-AFC is a highly specific substrate for the CLN2p/TPP-I assay. The fact that with this substrate the enzyme cleaves a peptide bond between the two amino acids may be the reason for the high level of specificity.

UV light synergistically enhances the cardiotoxic effects of interleukin 1beta through peroxynitrite formation.

BACKGROUND: Proinflammatory cytokines play an important role in chronic cardiac diseases. METHODS AND RESULTS: Neonatal rat cardiomyocytes were exposed to interleukin (IL)-1beta (2 ng/mL) for 4 days. We assessed contractility through videomicroscopy and calcium transients with the Ca(2+)-sensitive dye fura-2. In IL-1beta-treated cells, the UV excitation (380 nm) necessary to induce dye fluorescence effected a rapid cessation of Ca(2+) transients and contraction, accompanied by calcium overload originating from an intracellular compartment. This occurred in the absence of fura-2 but required UV illumination. Incubation with 10 mmol/L N-acetylcysteine prevented this response, suggesting a free radical-mediated event. However, exposure to IL-1beta either increased or did not change the activity of the free radical scavengers superoxide dismutase, catalase, and glutathione peroxidase. In contrast, lipid peroxidation increased by 600% (P < or =.0001) in the IL-1beta plus UV-treated cells, an effect eliminated by L-NMMA. L-NMMA also completely abolished the UV-mediated cytotoxicity. We used immunohistochemistry to localize nitrotyrosine accumulation in the myocytes cotreated with IL-1beta and UV, an effect that was also blocked by L-NMMA. CONCLUSIONS: We hypothesize that the toxic radical peroxynitrite, arising from nitric oxide and superoxide anion, may be responsible for tetany and acute cardiomyocyte death. These results demonstrate the potential role of peroxynitrite in cardiotoxicity, which may be important in cardiac diseases associated with proinflammatory cytokines.

Lysosomal ceroid depletion by drugs: therapeutic implications for a hereditary neurodegenerative disease of childhood.

Neuronal ceroid lipofuscinoses (NCLs) are the most common hereditary neurodegenerative diseases of childhood. The infantile form, INCL, is caused by lysosomal palmitoyl-protein thioesterase (PPT) deficiency, which impairs the cleavage of thioester linkages in palmitoylated proteins, preventing their hydrolysis by lysosomal proteinases. Consequent accumulation of these lipid-modified proteins (constituents of ceroid) in lysosomes leads to INCL. Because thioester linkages are susceptible to nucleophilic attack, drugs with this property may have therapeutic potential for INCL. We report here that two such drugs, phosphocysteamine and N-acetylcysteine, disrupt thioester linkages in a model thioester compound, [14C]palmitoyl approximately CoA. Most importantly, in lymphoblasts derived from INCL patients, phosphocysteamine, a known lysosomotrophic drug, mediates the depletion of lysosomal ceroids, prevents their re-accumulation and inhibits apoptosis. Our results define a novel pharmacological approach to lysosomal ceroid depletion and raise the possibility that nucleophilic drugs such as phosphocysteamine hold therapeutic potential for INCL.

Two common mutations in the CLN2 gene underlie late infantile neuronal ceroid lipofuscinosis.

Late infantile neuronal ceroid lipofuscinosis (LINCL) is one of the most common pediatric neuronal degenerative disorders. A candidate gene underlying this disease, designated CLN2, was recently cloned and the gene product was characterized as a lysosomal pepstatin-insensitive carboxypeptidase (LPIC). Four mutations were identified in CLN2 from three unrelated LINCL individuals. To investigate further the mutation frequency in LINCL, we screened 16 LINCL probands for these four mutations. The previously reported intronic mutation, T523-1 G-->C. was found in 56% (9/16) of the cases, of which two were homozygous and accounted for 34% (11/32) of LINCL chromosomes. The previously reported nonsense mutation, 636 C-->T leading to R208stop, was found in 31% (5/16) of the cases, including one homozygote and accounted for 19% (6/32) of LINCL chromosomes. Two previously described missense mutations, 1107 T-->C and 1108 G-->A, were not detected in any of these 16 probands. In total, the two observed mutations, T523-1 G-->C and 636 C-->T, accounted for 53% (17/32) of LINCL alleles. Thus, one or both mutations were seen in 11 (69%) cases and no mutation has yet been identified in five. Our finding that these two mutations are common in LINCL cases adds further evidence in support of the idea that dysfunction of LPIC underlies LINCL. Positive molecular testing can now complement clinical diagnosis of LPIC and will allow for pre-natal diagnosis for subsequent pregnancies.

Normal adaptive function with learning disability in duplication 8p including band p22.

Duplication 8p usually results in a syndrome characterized by profound mental retardation, mild facial anomalies, and malformations of hand, heart, and brain. We report on a large kindred segregating a Y;8 translocation in whom several individuals have duplication 8p22-->8pter. These individuals have normal adaptive function despite their unbalanced karyotype. The family was studied with G-banding and fluorescent in situ hybridization (FISH) using probes to chromosomes 8 and Y. Comparison of this family with other reported cases defines a mild clinical outcome for trisomy 8p22-->8pter in contrast to the severe findings when the duplication involves a longer, more proximal segment.

Molecular screening of Batten disease: identification of a missense mutation (E295K) in the CLN3 gene.

Batten disease, the juvenile form of neuronal ceroid lipofuscinosis, is a prevalent neuron degenerative disorder of childhood. A 1.02-kb genomic deletion in the Batten disease gene CLN3 has been determined to be a common mutation. We developed a PCR method to screen for this deletion and tested 43 Batten disease probands. We found 36% (31/86) of Batten disease chromosomes did not carry the 1.02-kb deletion. Of the three heterozygotes for the 1.02-kb deletion, a novel G-to-A missense mutation at nucleotide 1020 of the CLN3 cDNA sequence was found on two of the non-1.02-kb deletion chromosomes. The missense mutation resulted in a substitution of glutamic acid (E) by lysine (K) at position 295 (E295 K). The E295 K mutation causes a change in predicted local protein conformation. This glutamic acid is a highly conserved acidic amino acid, being present in human, mouse, dog and yeast, which suggests it may play an important role in the function of the Batten disease protein.

Atypical late infantile and juvenile forms of neuronal ceroid lipofuscinosis and their diagnostic difficulties.

We have collected 122 late-infantile neuronal ceroid lipofuscinosis (LINCL, CLN2) and 191 juvenile NCL (JNCL, CLN3) cases, diagnosed on the basis of age-at-onset, clinical symptomatology, and pathological findings and representing the most common forms of NCL in the United States, and Europe. However, careful analysis of available data revealed that about 80% of cases show typical and 20% show atypical clinical course and/or pathological findings and thus, may represent variants of LINCL and JNCL, respectively. Recent progress in the biochemistry and molecular genetics of NCL inclined us to reevaluate these atypical NCL cases. The gene responsible for LINCL has not yet been identified, except for the Finnish variant. Accumulation of subunit c of mitochondrial ATP synthase, to curvilinear profiles, is found in LINCL cases. A novel variant of LINCL, with predominantly granular profiles in the lysosomal storage, as well as normal excretion of subunit c in urine samples, was found in five cases. When the palmitoyle-protein thioesterase (PPT) was studied in these five cases, it was found that the level was deficient, suggesting that they are not LINCL, but the infantile form of neuronal ceroid lipofuscinosis (INCL). Using molecular genetic techniques in the typical JNCL cases, common 1.02 kb deletion to CLN3 was found in 23/27 (homozygotes) and in one allele 4/27 (heterozygotes) in affected pedigrees. In atypical JNCL pedigrees, it was found in 5/16 heterozygotes, while in 1/5 pedigrees, a novel mutation of one atypical JNCL where a single amino acid substitution at 295 E-->K was found in one allele. None of the atypical JNCL cases was homozygote. In atypical JNCL cases where mutation in CLN3 has not been identified (11/16 probands), several possibilities may exist. The phenotype may be caused by a yet undefined mutation in CLN3 or may be due to phenotypically overlapping with other forms of NCL. Pheno/genotypic correlation and the diagnostic difficulties are discussed.

Fragile X syndrome in two siblings with major congenital malformations.

We report on 2 brothers with both fragile X and VACTERL-H syndrome. The first sibling, age 5, had bilateral cleft lip and palate, ventricular septal defect, and a hypoplastic thumb. The second sibling, age 2 1/2, had a trachesophageal fistula, esophageal atresia, and vertebral abnormality. High-resolution chromosome analysis showed a 46, XY chromosome constitution in both siblings. By PCR and Southern blot analysis, the siblings were found to have large triplet repeat expansions in the fragile X gene (FMR 1) and both had methylation mosaicism. Enzyme kinetic studies of iduronate sulfatase demonstrated a two-fold increase in activity in the first sib as compared to the second. Possible mechanisms through which the fragile X mutation can cause down-regulation of adjacent loci are discussed.

A common mutation site in the beta-galactosidase gene originates in Puerto Rico.

Several mutation sites have been found in the beta-galactosidase gene of patients with GM1 gangliosidosis. In a previous report we found a common point mutation site in American patients with GM1 gangliosidosis resulting in a 208Arg --> Cys amino acid substitution. From the patients' family history, we suggested that this mutation may have come to South and North America via Puerto Rico. Four new patients with infantile GM1 gangliosidosis have been analyzed with allele-specific hybridization. Two siblings from Puerto Rico of Spanish ancestry are homozygous for this mutation. Another patient also from Puerto Rico is heterozygous for this allele, and another black patient does not have this mutation. These results support our initial hypothesis that this mutation has probably arisen in Puerto Rico.

Abnormal acid phosphatases in neuronal ceroid-lipofuscinoses.

Acid phosphatases in brain and cultured lymphoblasts from patients affected with neuronal ceroid-lipofuscinoses (NCL) were studied by starch gel electrophoresis. After electrophoresis the gel was incubated with 4-methyl umbelliferyl phosphate at pH 4.5 and the fluorescent reaction product was visualized under ultraviolet light. Control brain showed a single band with mobility of about 1 cm while NCL patients showed two additional fast moving bands. In the late-infantile, and in the adult form (Kufs disease), the middle band was prominent while the fast moving band was predominant in juvenile NCL. In long-term lymphoblasts, controls showed a single band of acid phosphatase activity while both juvenile and late-infantile NCL showed two additional fast moving bands. Obligate heterozygotes showed reduced levels of the fast moving bands. Fluorometric assay of acid phosphatase using 4-methylumbelliferyl phosphate as substrate showed a 2-fold increase in activity in the patients. The increased acid phosphatase activity is completely inhibited by tartrate. Lymphocyte hexosamnidase activities were unchanged in NCL patients lymphoblasts. Studies on brains of NCL patients and on cultured lymphoblasts from families with late-infantile and juvenile form of NCL showed that abnormal acid phosphatase is characteristic of NCL.

A de novo 13 nt deletion, a newly identified C647W missense mutation and a deletion of exon 18 in infantile onset glycogen storage disease type II (GSDII).

We identified the presumably rare event of de novo mutation in an autosomal recessive disorder, glycogen storage disease type II (GSDII). GSDII results from inherited deficiency of acid alpha-glucosidase (acid maltase) and both the expressed and structural gene (designated GAA) have been isolated. The mutation was a deletion of 13 nt of coding sequence (delta nt 1456-1468) on the paternally derived allele of the proband. The delta nt 1456-1468 results in a reading frameshift and a premature termination signal upstream of the enzyme catalytic site. Paternity was confirmed by presence of two downstream, uncommon amino acid substitutions (E689K, W746C) in both proband and father and by comparison of nine short tandem repeats. The maternal allele carried a newly identified deleterious C647W missense mutation in a highly conserved area of the protein. The C647W mutation was also found in a second unrelated proband, heteroallelic with a deletion extending from IVS17 to IVS18.

New X-linked mental retardation (XLMR) syndrome with distinct facial appearance and growth retardation.

We report on 2 brothers and their nephew with an apparently new X-linked mental retardation (XLMR) syndrome characterized by a distinct facial appearance, growth retardation, and severe mental retardation. The facial traits included triangular shape; bifrontal narrowness; malar flatness; blepharophimosis; very deeply set eyes; epicanthus inversus; bulbous nose; low hairline; low-set, deeply cupped, and protruding ears; short ill-defined philtrum; and thin tented upper lip. These facial anomalies are particularly striking and recognizable even at birth. The boys were small for gestational age and remained below -2 SD in growth parameters. With age, large joint contractures developed. Pectus excavatum was apparent at birth but became more obvious with age. Global developmental delay was evident in infancy. The brothers were nonverbal while their nephew spoke simple words. Optic atrophy, esotropia, nystagmus, and spastic diplegia were evident. They were self-abusive, hyperactive, and poorly coordinated. CT scans demonstrated atrophic hydrocephalus. No EEG abnormalities were detected. Karyotypes were 46,XY and fragile X negative. Routine chemistries; amino, organic, and uronic acids; oligosaccharides; lysosomal enzymes; and very long chain fatty acids were normal. Remarkable phenotypic similarity between these brothers and their nephew and lack of manifestations in their mothers makes X-linked recessive inheritance likely. This syndrome, which does not appear to have been reported previously, adds to the delineation of XLMR.

Molecular carrier testing for the fragile X syndrome: Issues for genetic counselors.

Molecular analysis of the fragile X (FMR-1) gene identifies female fragile X carriers, but appropriate genetic counseling can only be provided if the limitations of the testing methods are understood. Molecular analysis of this gene is achieved with both the polymerase chain reaction (PCR) and Southern blot techniques. PCR is faster and can determine the actual number of CGG repeats, which modifies genetic counseling substantially. However, for a sizeable percentage of women, PCR alone is not conclusive, and Southern analysis is necessary to complete the study. While this procedure takes longer, it is usually conclusive. Women who present for genetic counseling and carrier testing in the second trimester of pregnancy need this information quickly, and for them the turn-around time is paramount. It is critical that genetic counselors understand these methods so that they can educate their clients and facilitate appropriate follow-up.

Rapid fragile X carrier screening and prenatal diagnosis using a nonradioactive PCR test.

OBJECTIVE: To develop a rapid, nonradioactive test using the polymerase chain reaction (PCR) capable of detecting full fragile X mutations, premutations, and resolving normal alleles and to apply this to prenatal diagnosis and carrier screening of pregnant women at risk for fragile X carrier status. DESIGN: Prenatal and blood sample PCR analysis with confirmation by direct Southern blotting and cytogenetic techniques. SETTING: Samples sent to a DNA diagnostic research laboratory at a tertiary referral center. PARTICIPANTS: Pregnant women with a family history of undiagnosed mental retardation or known fragile X syndrome and controls. RESULTS: A rapid, nonradioactive PCR screening protocol for the fragile X mental retardation-1 gene for both normal and mutant alleles was developed. Analysis of 570 control X chromosomes showed a modal number of 30 CGG repeats (range, 12 to 52 repeats) and a calculated heterozygosity of approximately 80%. No excess of homozygosity was found, indicating the test was accurate for normal allele resolution. In addition, 150 unrelated pregnant women were screened. Within known fragile X families, five of 20 pregnant women were diagnosed as carriers. Two new fragile X families were diagnosed among relatives of 130 females with family histories of undiagnosed mental retardation, although no carriers were identified. Prenatal PCR testing of 28 carriers accurately detected nine fetuses with full mutations. CONCLUSIONS: This rapid, nonradioactive PCR protocol allows accurate resolution of normal alleles as well as simultaneous detection of carrier alleles and full mutations. With this approach, efficient screening of pregnant women at risk for fragile X carrier status, subsequent genetic counseling of identified carriers, and reliable prenatal diagnosis can be offered.

Metabolic studies in a mouse model of hepatorenal tyrosinemia: absence of perinatal abnormalities.

Radiation induced chromosomal deletions at the albino locus in the mouse, lethal when homozygous, cause abnormalities of expression of several unlinked liver specific genes. Recently, the gene encoding FAH was shown to be included in the deletions. Since in humans FAH mutations cause tyrosinemia type I, deletion homozygous mice were suspected of having tyrosinemia. Studies of plasma amino acids did not confirm this suspicion. Also, succinylacetone levels were normal in fetal and newborn livers of deletion homozygotes. The present evidence, therefore, does not support the assumption that the earlier described ultrastructural and enzyme abnormalities in deletion homozygotes are secondary effects of tyrosinemia caused by the deletion of FAH.