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PubMed1998

Juvenile rheumatoid arthritis and del(22q11) syndrome: a non-random association.

Del(22q11) is a common microdeletion syndrome with an extremely variable phenotype. Besides classical manifestations, such as velocardiofacial (Shprintzen) or DiGeorge syndromes, del(22q11) syndrome may be associated with unusual but probably causally related anomalies that expand its phenotype and complicate its recognition. We report here three children with the deletion and a chronic, erosive polyarthritis resembling idiopathic cases of juvenile rheumatoid arthritis (JRA). Patient 1, born in 1983, initially presented with developmental delay, facial dysmorphism, velopharyngeal insufficiency, and severe gastro-oesophageal reflux requiring G tube feeding. From the age of 3 years, he developed JRA, which resulted in severe restrictive joint disease, osteopenia, and platyspondyly. Patient 2, born in 1976, had tetralogy of Fallot and peripheral pulmonary artery stenosis. She developed slowly, had mild dysmorphic facial features, an abnormal voice, and borderline intelligence. JRA was diagnosed at the age of 5 years. The disorder followed a subacute course, with relatively mild inflammatory phenomena, but an extremely severe skeletal involvement with major osteopenia, restrictive joint disease (bilateral hip replacement), and almost complete osteolysis of the carpal and tarsal bones with phalangeal synostoses, leading to major motor impairment and confinement to a wheelchair. Patient 3, born in 1990, has VSD, right embryo-toxon, bifid uvula, and facial dysmorphism. She developed JRA at the age of 1 year. She is not mentally retarded but has major speech delay secondary to congenital deafness inherited from her mother. In the three patients, a del(22q11) was shown by FISH analysis. These observations, and five other recently published cases, indicate that a JRA-like syndrome is a component of the del(22q11) spectrum. The deletion may be overlooked in those children with severe, chronic inflammatory disorder.

Adult↗
PubMed1998

A molecular, cytogenetic, and clinical evaluation of mosaic tandem duplication 17p and Charcot-Marie-Tooth type 1A neuropathy.

An 8 year old girl with partial duplication of the short arm of chromosome 17 had a mosaic 46,XX,der(17)?del(17)(p12)dup(17) (p11.2p12).ish dup(17)(p11.2p13.3)(D17S 379x2, p53x2, D17S122x2, D17S29+) karyotype. The extent of mosaicism was 20% in lymphoblasts and 100% in fibroblasts. Fluorescence in situ hybridisation (FISH) proved invaluable in defining the abnormality precisely. The cytogenetic morphology by FISH assay ruled out a microdeletion of the Miller-Dieker syndrome (MDS) region. However, there was no MDS deletion but a duplication of this region. The duplication was extensive and included proximal p53 and D17S122, Charcot-Marie-Tooth type 1A (CMT1A), but not D17S29, the Smith-Magenis syndrome (SMS) region. This patient has the clinical features and generalised decreased peripheral nerve conduction velocity characteristic of CMT1A. The clinical management of paediatric cases of mosaic trisomy 17p cases would ential testing for CMT1A duplication. If duplicated, a decrease in nerve conduction velocity (NCV) of the peripheral motor neurones would be necessary to ensure the manifestation of CMT1A neuropathy. The parents of probands with delayed NCV should be counselled about the risk of CMT1A in later life.

Charcot-Marie-Tooth Disease↗
PubMed2001

Leucodystrophy and oculocutaneous albinism in a child with an 11q14 deletion.

We report a patient with an undetermined leucodystrophy associated with type 1A oculocutaneous albinism (OCA). Type 1 OCA results from recessive mutations in the tyrosinase gene (TYR) located in 11q14.3. The patient was found by FISH to carry a deletion of at least the first exon of the TYR gene on one chromosome and a (TG) deletion at codon 244/245 on the second chromosome. The existence of the microdeletion suggested that a gene responsible for leucodystrophy was located in the vicinity of the TYR gene. A combination of a test of hemizygosity and contig mapping studies allowed us to map the gene within a 0.6 cM region flanked by microsatellite markers D11S1780 and D11S931.

Adolescent↗
PubMed2003

The human Y chromosome's azoospermia factor b (AZFb) region: sequence, structure, and deletion analysis in infertile men.

Microdeletions of the Y chromosome long arm are the most common mutations in infertile males, where they involve one or more "azoospermia factors" (AZFa, b, and c). Understanding of the AZF structure and gene content and mapping of the deletion breakpoints in infertile men are still incomplete. We have assembled a complete 4.3 Mb map of AZFb and surrounding regions by means of 38 BAC clones. The proximal part of AZFb consists of large repeated sequences organised in palindromes, but most of it is single copy sequence. A number of known and novel genes and gene families map in this interval, and most of them are testis specific or have testis specific transcripts. STS mapping allowed us to identify four severely infertile subjects with a deletion in AZFb with similar breakpoints, therefore suggesting a common deletion mechanism. This deletion includes at least five single copy genes and two duplicated genes, but does not remove the historical AZFb candidate gene RBMY1. These data suggest that other genes in AZFb may have important roles in spermatogenesis. We had no evidence for homologous recombination between large repeats as a possible deletion mechanism, as shown for AZFa and AZFc. However, identical sequences in AZFb and AZFc exist, and this finding could explain deletions found in these regions.

Chromosome Breakage↗
PubMed2003

Disruption of the neuronal PAS3 gene in a family affected with schizophrenia.

Schizophrenia and its subtypes are part of a complex brain disorder with multiple postulated aetiologies. There is evidence that this common disease is genetically heterogeneous, with many loci involved. In this report, we describe a mother and daughter affected with schizophrenia, who are carriers of a t(9;14)(q34;q13) chromosome. By mapping on flow sorted aberrant chromosomes isolated from lymphoblast cell lines, both subjects were found to have a translocation breakpoint junction between the markers D14S730 and D14S70, a 683 kb interval on chromosome 14q13. This interval was found to contain the neuronal PAS3 gene (NPAS3), by annotating the genomic sequence for ESTs and performing RACE and cDNA library screenings. The NPAS3 gene was characterised with respect to the genomic structure, human expression profile, and protein cellular localisation to gain insight into gene function. The translocation breakpoint junction lies within the third intron of NPAS3, resulting in the disruption of the coding potential. The fact that the bHLH and PAS domains are disrupted from the remaining parts of the encoded protein suggests that the DNA binding and dimerisation functions of this protein are destroyed. The daughter (proband), who is more severely affected, has an additional microdeletion in the second intron of NPAS3. On chromosome 9q34, the translocation breakpoint junction was defined between D9S752 and D9S972 and no genes were found to be disrupted. We propose that haploinsufficiency of NPAS3 contributes to the cause of mental illness in this family.

ATP-Binding Cassette Transporters↗
PubMed1999

Psychiatric inpatients and chromosome deletions within 22q11.2.

Velocardiofacial syndrome (VCFS) is a congenital disorder characterised by multiple dysmorphisms, cleft palate, cardiac anomalies, and learning disabilities due to a microdeletion of chromosome 22q11.2. Although VCFS is often associated with psychiatric symptoms, its prevalence among psychiatric patients is unknown. A total of 326 patients admitted in September and October 1997 to a Japanese psychiatric hospital were screened for the clinical features of VCFS. Twelve patients with minor facial dysmorphia were identified; chromosomal analysis with fluorescent in situ hybridisation (FISH) was performed in six patients who, further assessment suggested, were most likely to have VCFS. Chromosome 22q11.2 deletion was identified in a 41 year old woman who had symptoms of schizophrenia but no major dysmorphia, such as cardiovascular anomalies and cleft palate. Her behavioural and neuropsychological profiles were similar to those previously reported in VCFS. She was hemizygous for the FISH probe N25 (GDB locus D22S75) and also for probes N72H9 (D22S181), sc11.1a, C443 (D22S941), sc4.1 (D22S134), sc11.1b, N19B3 (D22S264), N122B5 (D22S934), and N77F7 (D22S939). The size of the deletion was about 3 Mb. Our patient had only some features of VCFS including a square nasal root, hypernasal speech, and hypoparathyroidism. She did, however, have the common larger deletion of type A. This finding suggests that psychiatric symptoms in VCFS can occur without major developmental symptoms such as cardiovascular anomalies and cleft palate. Additional patients with schizophrenia may have subtle features of VCFS which are unrecognised on routine medical examinations.

Abnormalities, Multiple↗
PubMed1997

Velocardiofacial syndrome.

Velocardiofacial syndrome is a syndrome of multiple anomalies that include cleft palate, cardiac defects, learning difficulties, speech disorder and characteristic facial features. It has an estimated incidence of 1 in 5000. The majority of cases have a microdeletion of chromosome 22q11.2. The phenotype of this condition shows considerable variation, not all the principal features are present in each case. Identification of the syndrome can be difficult as many of the anomalies are minor and present in the general population.

Abnormalities, Multiple↗
PubMed1998

[Natural hybridization between two subspecies of the house mouse, Mus musculus domesticus and Mus musculus castaneus, near Lake Casitas, California].

The house mouse Mus musculus is a polytypic species, distributed worldwide, with three main subspecies: M. m. musculus in the North-East of Eurasia, M. m. castaneus in South-East Asia, and M. m. domesticus in Europe, the Near-East, and Africa. This last subspecies may also be found in Australia and the Americas, where it was brought by European colonization. Previous studies, however, have shown the presence of specific antiviral determinants of Asian origin in a mouse population at Lake Casitas, California. In this study, an analysis of the variability at 35 enzyme loci demonstrates the hybrid nature of this Californian population intermediate between M. m. castaneus and M. m. musculus. Restriction fragment length polymorphisms of two fragments of the mitochondrial DNA also confirm unambiguously the presence of two types of matrilines in comparable frequencies in our sample. Nevertheless, the study of a subspecies-specific Y chromosome microdeletion in the Zfy2 gene reveals only the M. m. domesticus haplotype at Lake Casitas, a phenomenon comparable with the one observed in other hybrid zones of the M. musculus complex. These findings testify once more that genetic exchanges between subspecies inside the broader M. musculus gene pool are still possible.

Animals↗
PubMed2006

[Holt-Oram syndrome: characterization of a novel mutation].

INTRODUCTION: Cardiomyelic syndromes encompass congenital heart disease and skeletal malformations of the upper limbs and are related to mutations in transcription factors with T-Box domains. Holt-Oram syndrome is caused by a dominant mutation in the TBX5 gene that alters the three-dimensional structure of the protein and its DNA binding function. Several point mutations and deletions in TBX5 have been reported in patients with the Holt-Oram syndrome phenotype. PATIENTS AND METHODS: The proband was a boy with a large atrial septal defect ostium secundum type and a ventricular septal defect, diagnosed by clinical findings (heart murmur) and echocardiography. He also presented slightly hypoplastic thumbs with distal bilateral placement and an implantation index of 0.19 (compared with an average of 0.50 for his gestational age at birth). The boy was referred to the department of medical genetics to rule out 22q11.2 microdeletion syndrome. RESULTS: Karyotype and fluorescence in situ hybridization at locus D22S75 were both normal. Because of his clinical findings, molecular study for Holt-Oram syndrome was indicated, leading to the finding of a mutation at intron 7 of TBX5, probably producing a splicing alteration of the gene and resulting in a protein truncated at its C-terminal end. The proband's parents presented the wild type sequence of the gene, thus indicating that the mutation was produced de novo, although a possible germinal mosaicism in the parents could not be ruled out. CONCLUSIONS: Holt-Oram syndrome is the most frequent cause of cardiomyelic syndrome. All children with heart malformations and abnormalities of the upper limbs such as absent, hypoplastic, distally placed or triphalangic thumbs should undergo molecular studies for this syndrome.

Abnormalities, Multiple↗
PubMed1999

Identification of GTF2IRD1, a putative transcription factor within the Williams-Beuren syndrome deletion at 7q11.23.

Williams-Beuren syndrome (WBS) is a microdeletion syndrome caused by haploinsufficiency of genes at 7q11.23. Here we describe the identification and characterization of a novel gene named GTF2IRD1, for GTF2I-repeat domain 1, within the WBS deletion region. Northern blot analysis revealed ubiquitous expression during development with two transcripts of 3.6 kb and 5.0 kb generated by alternative splicing. GTF2IRD1 encodes a protein of 944 amino acids that contains a region of high similarity to a unique motif with helix-loop-helix forming potential occurring within the transcription factor GTF2I. Analogous to TFII-I, the product of GTF2IRD1 may have the ability to interact with other HLH-proteins and function as a transcription factor or as a negative transcriptional regulator. A recent report of the identification of a muscle-specific transcription factor, MusTRD1, supports this hypothesis (O'Mahoney et al., 1998). The open reading frame described for MusTRD1 is identical to that of GTF2IRD1; however, the putative MusTRD1-protein is 486 amino acids shorter than the predicted protein encoded by GTF2IRD1. A heterozygous deletion of GTF2IRD1 may contribute to the complex WBS phenotype.

Amino Acid Sequence↗
PubMed2000

Characterization of a new TSPY gene family member in Yq (TSPYq1).

We investigated subinterval 6E on the human Y chromosome, a region frequently deleted in infertile males. YAC yOX17, mapped within subinterval 6E by STS-PCR, was analyzed for the presence of new genes. TSPYq1, a member of the TSPY multi-copy gene family, was isolated and characterized from a yOX17 cosmid subclone. PCR and FISH analysis performed on normal subjects and on patients with microdeletions of Yq suggested the presence of multiple copies of TSPY in Yq.

Amino Acid Substitution↗
PubMedDate not supplied

Prenatal diagnosis of smith-magenis syndrome (del 17p11.2).

Smith-Magenis syndrome is associated with a microdeletion of the short arm of chromosome 17 with phenotypic abnormalities including dysmorphic facies, self-injurious behavior, mental and neurologic disturbances, and congenital cardiac defects. The majority of patients present in mid-childhood or adulthood. We describe a fetus in which the diagnosis of Smith-Magenis syndrome was made at 16 weeks of gestation following amniocentesis for increased risk for Down syndrome detected by second-trimester maternal serum screening. Ultrasound evaluation revealed multiple fetal anomalies. The pregnancy was terminated at 20 weeks of gestation. Post-mortem findings included dysmorphic facial features, tetralogy of Fallot, a thymic duct remnant, pancreatic islet cell hyperplasia, and abnormal lung fissuring. This represents the second case of prenatally diagnosed Smith-Magenis syndrome. Molecular genetic techniques in the diagnosis of the Smith-Magenis syndrome and other small deletions are becoming an important tool in the genetic evaluation of ultrasound abnormalities.

Abnormalities, Multiple↗
PubMed1998

Molecular dissection of Norrie disease.

Norrie disease (ND) is a severe form of congenital blindness accompanied by mental retardation and/or deafness in at least one third of the patients. This article summarizes advances in the molecular genetic analysis of this disease during the last 13 years, including mapping and cloning of the human gene and the generation and characterization of a mouse model. Genetic linkage studies and physical mapping strategies have assigned the ND locus to the proximal short arm of the human X chromosome. The identification of chromosomal rearrangements in several patients, such as microdeletions, enabled the isolation of the ND gene by a positional cloning approach. Numerous point mutations in this gene have been identified in three distinct clinical entities: (1) ND, (2) familial and sporadic exudative vitreoretinopathy, and (3) retinopathy of prematurity. The gene encodes a relatively small protein, consisting of 133 amino acids. The function of the gene product is yet unknown, although homologies with known proteins and molecular modelling data suggest a role in the regulation of cell interaction or differentiation processes. A mouse model has been generated to shed more light on early pathogenic events involved in ND and allelic disorders. The mouse homologous protein is highly identical (94%) to the human polypeptide. The gene is expressed in the neuronal layers of the mouse retina, the cerebellum and olfactory epithelium. Mutant mice show snowflake-like opacities within the vitreous, dysgenesis of the ganglion cell layer and occasionally degeneration of photoreceptor cells. The mouse phenotype does not include phthisis bulbi and, overall, resembles a mild form of ND. Electrophysiological studies revealed a severely altered electroretinogram b-wave. These results suggest a primary defect in the inner neuronal layers of the retina. Defects in the vitreous and photoreceptor cell layer are most likely secondary effects. Further histological, functional and molecular studies of the mouse model are needed to provide additional information on disease associated pathways.

Animals↗
PubMedDate not supplied

Is intracytoplasmic sperm injection itself an indication to perform preimplantation genetic diagnosis (PGD)? About PGD, invasive prenatal diagnosis and genetic sonography.

Intracytoplasmic sperm injection (ICSI) provides the only sufficient treatment to overcome severe forms of male infertility. However, male infertility is linked to several genetic problems as an increased number of chromosomal aberrations, cystic fibrosis transmembrane conductance regulator gene mutations, Y-chromosome microdeletions, and androgen receptor mutations. Therefore, these couples are at a higher risk of transmitting genetic problems to their offspring compared to the general population. A proposed increased number of gonosomal aberrations in the offspring possibly results from the ICSI technique itself. This led in general to a worldwide agreement to counsel those couples to undergo invasive prenatal diagnosis in order to exclude chromosome abnormalities, especially gonosomal aberrations. In this paper the genetic risks of these couples and the possible implications of ICSI itself are discussed. Preimplantation genetic diagnosis may be considered a procedure of choice in these cases, but substantial ethical problems arise when such a screening is sought. An alternative procedure of prenatal diagnosis in these couples seems to be 'genetic sonography', i.e. high-resolution ultrasound with measurement of nuchal translucency at the end of the first trimester, and detailed fetal evaluation at 18-22 weeks of gestation.

Chromosome Aberrations↗
PubMedDate not supplied

Mild ventriculomegaly as a counselling challenge.

OBJECTIVE: Our purpose was to evaluate the outcome of a group of fetuses with mild ventriculomegaly. METHODS: We retrospectively collected all cases of antenatally diagnosed mild enlargement of the lateral cerebral ventricles (transverse diameter of the atrium between 10 and 15 mm) between 1992 and 1997. Cases were included in the study if no other ultrasonic anomalies (including soft markers) were found. TORCH screening, karyotyping, search for associated anomalies and neurological examination (including imaging) were performed. Outcome information was available for all cases up to 30 months. RESULTS: Fourteen cases were examined. TORCH was always negative, 1 case with a microdeletion of chromosome 1 was identified. During the course of pregnancy, 2 fetuses showed progression to frank hydrocephalus. Five cases of agenesis of the corpus callosum, 1 of lissencephaly and 1 of heterotopia were eventually diagnosed. After birth 2 syndromes were identified. Three babies died during the follow-up period, among the survivors 4 had severe neurological damage, 2 of them had no associated dysmorphic findings. DISCUSSION: A heterogeneous group of central nervous system disorders may manifest antenatally as mild ventriculomegaly. The current management may not be able to identify dangerous conditions that present subtle dysmorphic features, or be able to predict abnormal outcome in most of the cases.

Adult↗
PubMed2002

Segmental neurofibromatosis.

Segmental neurofibromatosis is characterised by a limited, segmental distribution of cutaneous neurofibromatosis type 1 (NF1) lesions. It has been suggested that segmental NF results from a postzygotic NF1 gene mutation, and, recently, this hypothesis has been proven in a patient with regionally distributed café-au-lait (CAL) spots and freckles by demonstrating an NF1 microdeletion restricted to fibroblasts cultured from CAL spots. We describe here a patient with segmental NF in which we could not demonstrate any NF1 gene mutation in fibroblasts cultured from neurofibromas by use of the protein truncation test, enzymatic mutation detection and fluorescence in situ hybridisation. These data are in line with the concept that NF1 mutations in Schwann cells, but not in fibroblasts, correlate with neurofibroma formation.

Humans↗
PubMed2005

Genomic structure and paralogous regions of the inversion breakpoint occurring between human chromosome 3p12.3 and orangutan chromosome 2.

Intrachromosomal duplications play a significant role in human genome pathology and evolution. To better understand the molecular basis of evolutionary chromosome rearrangements, we performed molecular cytogenetic and sequence analyses of the breakpoint region that distinguishes human chromosome 3p12.3 and orangutan chromosome 2. FISH with region-specific BAC clones demonstrated that the breakpoint-flanking sequences are duplicated intrachromosomally on orangutan 2 and human 3q21 as well as at many pericentromeric and subtelomeric sites throughout the genomes. Breakage and rearrangement of the human 3p12.3-homologous region in the orangutan lineage were associated with a partial loss of duplicated sequences in the breakpoint region. Consistent with our FISH mapping results, computational analysis of the human chromosome 3 genomic sequence revealed three 3p12.3-paralogous sequence blocks on human chromosome 3q21 and smaller blocks on the short arm end 3p26-->p25. This is consistent with the view that sequences from an ancestral site at 3q21 were duplicated at 3p12.3 in a common ancestor of orangutan and humans. Our results show that evolutionary chromosome rearrangements are associated with microduplications and microdeletions, contributing to the DNA differences between closely related species.

Animals↗
PubMed2006

Imprinting defects on human chromosome 15.

The Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are two distinct neurogenetic diseases that are caused by the loss of function of imprinted genes on the proximal long arm of human chromosome 15. In a few percent of patients with PWS and AS, the disease is due to aberrant imprinting and gene silencing. In patients with PWS and an imprinting defect, the paternal chromosome carries a maternal imprint. In patients with AS and an imprinting defect, the maternal chromosome carries a paternal imprint. Imprinting defects offer a unique opportunity to identify some of the factors and mechanisms involved in imprint erasure, resetting and maintenance. In approximately 10% of cases the imprinting defects are caused by a microdeletion affecting the 5' end of the SNURF-SNRPN locus. These deletions define the 15q imprinting center (IC), which regulates imprinting in the whole domain. These findings have been confirmed and extended in knock-out and transgenic mice. In the majority of patients with an imprinting defect, the incorrect imprint has arisen without a DNA sequence change, possibly as the result of stochastic errors of the imprinting process or the effect of exogenous factors.

Angelman Syndrome↗