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PubMed2003

Application of intracytoplasmic sperm injection in assisted reproductive technologies.

Intracytoplasmic sperm injection (ICSI) entails the mechanical insertion of a chosen spermatozoon directly into the cytoplasm of an oocyte. Due to the consistent fertilization and pregnancy outcome, ICSI is routinely used to treat azoospermic patients where spermatozoa are retrieved by epididymal aspiration or testicular biopsy. Since male subfertility has been associated with a higher incidence of genomic defects, ranging from numerical chromosomal abnormalities to Yq microdeletions, concerns have been raised as to the risk of transmitting genetic defects to the offspring. Screening for such defects can provide invaluable information for appropriate counselling prior to ICSI treatment. In order to address these concerns, a follow-up of the children born after ICSI treatment was conducted.

Adult↗
PubMed2006

Coexistence of peripheral primitive neuroectodermal tumor and tetralogy of Fallot.

We describe a little girl with tetralogy of Fallot (TOF) who was found to have a huge peripheral primitive neuroectodermal tumor (pPNET) when she developed progressive difficulty in standing and crawling at the age of 11 months. The tumor was located in the left paraspinal region (T4-T12), with intraspinal extension causing severe compression. Nine days after surgical decompression with laminectomy, chemotherapy was initiated with alternative courses of vincristine, doxorubicin, cyclophosphamide, etoposide, and ifosfamide every 3 weeks. The muscle power in her legs recovered substantially after 2 courses of chemotherapy. Although peripheral blood for cytogenetic study revealed no chromosome abnormality, recent cytogenetic analysis has revealed a high frequency of reciprocal translocation t(11;22)(q24;q12) detected in pPNET and a strong association between TOF and chromosome 22q11 microdeletion (del 22q11). Both genetic defects involve chromosome 22q in the close region. This case report illustrates the necessity of investigating for cytogenetic change in chromosome 22 and close follow-up due to the possibility of subsequent development of malignancies in patients with TOF.

Chromosome Aberrations↗
PubMed1999

Visual evoked potential evidence of albino-like chiasmal misrouting in a patient with Angelman syndrome with no ocular features of albinism.

An 8-month-old boy with global developmental delay, including visual and hearing inattention, was examined in the ophthalmic clinic. Monocular flash visual evoked potentials demonstrated a crossed asymmetry in scalp distribution, a feature considered to be pathognomic of albinism. Remarkably a foveal reflex was noted in each eye and this patient did not have nystagmus, iris transillumination, nor conspicuously pale fundi. The optic discs appeared normal. He was noted to have very fair skin and hair, with a small head and flat occiput. Cytogenetic studies demonstrated a microdeletion of the maternal chromosome 15q11-q13, and he was diagnosed with Angelman syndrome.

Albinism↗
PubMed2000

Surgical approach to complicated cervical aortic arch: anatomic, developmental, and surgical considerations.

BACKGROUND: Abnormalities of brachiocephalic arterial branching and arch laterality are common in patients with a cervical aortic arch. In addition, structural anomalies of the arch such as obstruction, aneurysms, and tortuosity are found in a significant number of cases. METHODS: Between 1990 and 1998, 6 patients underwent surgery for an obstructed right cervical arch. A significant obstruction was present at the transverse or distal arch in all patients, and was recurrent after previous repair in 2. In 1 patient, there was also a multi-lobed aneurysm of the aortic segment contiguous to the obstruction, and in 2 there was marked tortuosity of the arch. In all cases, the order of origin of the head and neck vessels was abnormal, and obstruction of 1 or more brachiocephalic vessels was found in 3. A vascular ring was present in all patients, with a right aortic arch and aberrant left subclavian artery in 4 patients and a double aortic arch with a dominant right cervical arch in 2. The descending aorta was circumflex (left-sided) in 3 patients. Three patients were repaired through a standard right posterolateral thoracotomy, and 3 through a median sternotomy. Patch augmentation aortoplasty was used in 2 patients, a tube graft from the ascending to descending aorta in 2, end to side anastomosis of the descending aorta to the proximal arch in 1, and direct anastomosis to reconstruct an atretic left-sided component of a double arch in 1. RESULTS: Repair was successful in all cases, with no perioperative complications. At follow-up ranging from 1 to 9 years, all patients were alive and well, with no recurrence of arch obstruction or other significant complications. Fluorescent in situ hybridization revealed microdeletion of chromosome 22q11 in 1 patient (not performed in the others). CONCLUSIONS: Structural anomalies of the arch are relatively common in patients with a cervical aortic arch. Such abnormalities may be the result of hemodynamic conditions and/or abnormal vascular tissue related either to the cervical position of the arch or its embryologic precursors. Given the highly variable anatomy of patients with a complicated cervical aortic arch, surgical considerations will vary in kind.

Adolescent↗
PubMed2005

Duplication of the 22q11.2 region associated with congenital cardiac disease.

The DiGeorge, or velocardiofacial, syndrome has been aetiologically linked to heterozygous deletion of the q11.2 region of chromosome 22. It is the most common of the microdeletion syndromes, and is associated with malformations involving the ventricular outflow tracts. Duplication of the 22q11.2 region has also been reported, adding to a growing list of syndromes involving genomic deletion or duplication that cause disease by decreasing or increasing the gene dosage. We report two cases of congenital cardiac disease associated with microduplications of 22q11.2, and discuss the evidence to date for the potential clinical significance of this genetic defect.

Female↗
PubMed2005

Prader-Willi syndrome: clinical genetics, cytogenetics and molecular biology.

Prader-Willi syndrome (PWS) is a neurodevelopmental disorder that arises from lack of expression of paternally inherited genes known to be imprinted and located in the chromosome 15q11-q13 region. PWS is considered the most common syndromal cause of life-threatening obesity and is estimated at 1 in 10,000 to 20,000 individuals. A de novo paternally derived chromosome 15q11-q13 deletion is the cause of PWS in about 70% of cases, and maternal disomy 15 accounts for about 25% of cases. The remaining cases of PWS result either from genomic imprinting defects (microdeletions or epimutations) of the imprinting centre in the 15q11-q13 region or from chromosome 15 translocations. Here, we describe the clinical presentation of PWS, review the current understanding of causative cytogenetic and molecular genetic mechanisms, and discuss future directions for research.

Chromosome Aberrations↗
PubMed2006

Beckwith-Wiedemann syndrome: multiple molecular mechanisms.

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth condition with an increased risk of developing embryonic tumours, such as Wilms' tumour. The cardinal features are abdominal wall defects, macroglossia and gigantism. BWS is generally sporadic; only 10-15% of cases are familial. A variety of molecular aberrations have been associated with BWS. The only mutations within a gene are loss-of-function mutations in the CDKN1C gene, which codes for an imprinted cell-cycle regulator. CDKN1C mutations appear to be particularly associated with umbilical abnormalities, but not with increased predisposition to Wilms' tumour. In the remaining BWS subgroups, a disturbance of the tight epigenetic regulation of gene expression (patUPD 11p, microdeletions or epimutations) seems to be the cause of the syndrome. Here we describe the clinical presentation of BWS and its dissociation from phenotypically overlapping overgrowth syndromes. We then review the current concepts of causative molecular genetic and epigenetic mechanisms, and discuss future directions of research.

Animals↗
PubMed1999

[Is sterility a genetic burden?].

Genetic causes of infertility are probably not rare. Today only a fraction of genes directly or indirectly involved in reproduction including sex determination and differentiation are known. Nevertheless, the list of well-defined genetic disorders impairing fertility is impressing already today and growing rapidly. Gonosomal aneuploidy and structural rearrangements represent a significant portion of the genetic causes of infertility in both sexes. Other chromosomal conditions include autosomal balanced structural changes (e.g. translocations), probably due to pairing disturbances of the affected chromosomes during meiosis. Some fundamental mechanisms in sex determination and differentiation have been characterized in recent years. Mutations in some of the genes involved in this process may lead to familial infertility. Genetic defects in gametogenesis of both sexes are currently being investigated using mouse models. Male specific causes of infertility include microdeletion within the AZF region of the euchromatic part of the long arm of the Y chromosome and obstructive azoospermia due congenital aplasia of the vas deferens in the presence of mutations in the CFTR gene.

Animals↗
PubMed2001

[Fetal and genetic aspects of congenital heart disease].

Fetal cardiology includes the assessment of the fetal heart for congenital heart disease (CHD) and arrhythmias, the management of affected fetuses, including parental counselling for the therapeutic options, the planning of the delivery and the postnatal care. This requires a close collaboration between obstetricians, neonatologists and pediatric cardiologists. Because of restricted financial sources extensive fetal echocardiographic assessment is reserved for pregnancies with increased risk for CHD, which includes a family history of CHD, suspicion of a cardiac or extracardiac fetal abnormalities at obstetric routine ultrasonography, fetal arrhythmias and chromosomal anomalies. Since most CHD occur in pregnancies without increased risk an ultrasound screening of the fetal heart during routine pregnancy ultrasound is recommended. Most forms of CHD can potentially be detected in utero, especially the severe ones with considerable fetal and postnatal morbidity and mortality. The prenatal diagnosis of a major cardiac malformation requires further assessments for extracardiac and chromosomal disorders. The deliveries of patients with major cardiac anomalies in a tertiary obstetric center close to a pediatric cardiac facility allows optimal perinatal and postnatal management. This may be of crucial importance for cardiac malformations which are arterial duct dependent postnatally. Many CHD have genetic causes. Well established is the association of CHD and the trisomies 13, 18 and 21, as well as the monosomy XO (Turner syndrome). During the last years more and more molecular genetic causes for CHD could be demonstrated. The most significant one is the microdeletion 22q11 syndrome (CATCH 22 syndrome), which is associated with different conotruncal anomalies. Also for various other congenital cardiac malformations and syndromes a genetic cause could be demonstrated. The search for genetic cofactors is important as it affects parental counselling and patient care.

Female↗
PubMed1998

22q11.2 deletions in a series of patients with non-selective congenital heart defects: incidence, type of defects and parental origin.

Previous studies have indicated a wide spectrum of incidences of 22q11.2 deletions in isolated and syndromic (sporadic or familial) cases of conotruncal heart defects, whereby the detection rate of the deletion varied from 65% in one study to 0 in another. We analysed 110 patients with non-selective syndromic or isolated non-familial congenital heart malformations by fluorescence in situ hybridization (FISH) using the D22S75 DiGeorge chromosome (DGS) region probe. A 22q11.2 microdeletion has been detected in 9/51 (17.6%) syndromic patients. Five were of maternal origin and four of paternal origin. None of the 59 patients with isolated congenital cardiac defect had a 22q11.2 deletion. We compared the cardiac anomalies of our patients with a 22q11.2 deletion with those of previously published series and we describe types of congenital heart defects which appear to be often associated with a 22q11.2 deletion. The ability to detect such types of heart defects and to provide an early diagnosis of 22q11.2 deletion is particularly relevant in very young infants, who often show only very mild expression of the otherwise well-characterized phenotypes of the DiGeorge/velo-cardio-facial syndrome (DG/VCFS).

Adolescent↗
PubMed2001

Brachytelephalangic dwarfism due to the loss of ARSE and SHOX genes resulting from an X;Y translocation.

Here we report an 8-year-old male patient who had mesomelic shortening of forearms and legs, brachytelephalangia and ichthyotic skin lesions. Chromosomal analysis showed an X;Y translocation involving the short arm of the X chromosome (Xp). Fluorescence in situ hybridization (FISH) and molecular studies localized the breakpoints on Xp22.3 in the immediate vicinity of the KAL gene demonstrating deletions of steroid sulfatase (STS), arylsulfatase E (ARSE), and short stature homeo box (SHOX) genes. It was suspected that the patient was suffering from chondrodysplasia punctata because of a loss of the arylsulfatase E (ARSE) gene. However, no stippled epiphyses were to be seen in the neonatal radiograph. Interestingly, this patient is the first case with a proven loss of the ARSE gene without chondrodysplasia punctata, assuming that chondrodysplasia punctata is not an obligatory sign of ARSE gene loss. Brachytelephalangia was the only result of ARSE gene deletion in this case. The patient's mother also had dwarfism and showed Madelung deformity of the forearms. She was detected as a carrier of the same aberrant X chromosome. The male patient did not show Madelung deformity, demonstrating that Lerri-Weill syndrome phenotype may be still incomplete in children with SHOX gene deletion. The wide clinical spectrum in the male and the Leri-Weill phenotype in his mother are the results of both a deletion involving several sulfatase genes in Xp22.3 and the SHOX gene located in the pseudoautosomal region. Nevertheless, there is no explanation for the absence of chondrodysplasia punctata despite the total loss of the ARSE gene. Further studies are necessary to investigate genotype/phenotype correlation in cases with translocations or microdeletions on Xp22.3, including the ARSE and the SHOX gene loci.

Arylsulfatases↗
PubMed2004

Causes of azoospermia and their management.

Azoospermia may occur because of reproductive tract obstruction (obstructive azoospermia) or inadequate production of spermatozoa, such that spermatozoa do not appear in the ejaculate (non-obstructive azoospermia). Azoospermia is diagnosed based on the absence of spermatozoa after centrifugation of complete semen specimens using microscopic analysis. History and physical examination and hormonal analysis (FSH, testosterone) are undertaken to define the cause of azoospermia. Together, these factors provide a >90% prediction of the type of azoospermia (obstructive v. non-obstructive). Full definition of the type of azoospermia is provided based on diagnostic testicular biopsy. Obstructive azoospermia may be congenital (congenital absence of the vas deferens, idiopathic epididymal obstruction) or acquired (from infections, vasectomy, or other iatrogenic injuries to the male reproductive tract). Couples in whom the man has congenital reproductive tract obstruction should have cystic fibrosis (CF) gene mutation analysis for the female partner because of the high risk of the male being a CF carrier. Patients with acquired obstruction of the male reproductive tract may be treated using microsurgical reconstruction or transurethral resection of the ejaculatory ducts, depending on the level of obstruction. Alternatively, sperm retrieval with assisted reproduction may be used to effect pregnancies, with success rates of 25-65% reported by different centres. Non-obstructive azoospermia may be treated by defining the cause of low sperm production and initiating treatment. Genetic evaluation with Y-chromosome microdeletion analysis and karyotype testing provides prognostic information in these men. For men who have had any factors potentially affecting sperm production treated and remain azoospermic, sperm retrieval from the testis may be effective in 30-70% of cases. Once sperm are found, pregnancy rates of 20-50% may be obtained at different centres with in vitro fertilisation and intracytoplasmic sperm injection.

Azoospermia↗
PubMed1999

Spontaneous functional correction of homozygous fanconi anaemia alleles reveals novel mechanistic basis for reverse mosaicism.

Somatic mosaicism due to reversion of a pathogenic allele to wild type has been described in several autosomal recessive disorders. The best known mechanism involves intragenic mitotic recombination or gene conversion in compound heterozygous patients, whereby one allele serves to restore the wild-type sequence in the other. Here we document for the first time functional correction of a pathogenic microdeletion, microinsertion and missense mutation in homozygous Fanconi anaemia (FA) patients resulting from compensatory secondary sequence alterations in cis. The frameshift mutation 1615delG in FANCA was compensated by two additional single base-pair deletions (1637delA and 1641delT); another FANCA frameshift mutation, 3559insG, was compensated by 3580insCGCTG; and a missense mutation in FANCC(1749T-->G, Leu496Arg) was altered by 1748C-->T, creating a cysteine codon. Although in all three cases the predicted proteins were different from wild type, their cDNAs complemented the characteristic hypersensitivity of FA cells to crosslinking agents, thus establishing a functional correction to wild type.

Alleles↗
PubMed1998

Mutations in a gene encoding a novel protein tyrosine phosphatase cause progressive myoclonus epilepsy.

Lafora's disease (LD; OMIM 254780) is an autosomal recessive form of progressive myoclonus epilepsy characterized by seizures and cumulative neurological deterioration. Onset occurs during late childhood and usually results in death within ten years of the first symptoms. With few exceptions, patients follow a homogeneous clinical course despite the existence of genetic heterogeneity. Biopsy of various tissues, including brain, revealed characteristic polyglucosan inclusions called Lafora bodies, which suggested LD might be a generalized storage disease. Using a positional cloning approach, we have identified at chromosome 6q24 a novel gene, EPM2A, that encodes a protein with consensus amino acid sequence indicative of a protein tyrosine phosphatase (PTP). mRNA transcripts representing alternatively spliced forms of EPM2A were found in every tissue examined, including brain. Six distinct DNA sequence variations in EPM2A in nine families, and one homozygous microdeletion in another family, have been found to cosegregate with LD. These mutations are predicted to cause deleterious effects in the putative protein product, named laforin, resulting in LD.

Alternative Splicing↗
PubMed1998

Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism.

Parkinson's disease is a common neurodegenerative disease with complex clinical features. Autosomal recessive juvenile parkinsonism (AR-JP) maps to the long arm of chromosome 6 (6q25.2-q27) and is linked strongly to the markers D6S305 and D6S253; the former is deleted in one Japanese AR-JP patient. By positional cloning within this microdeletion, we have now isolated a complementary DNA done of 2,960 base pairs with a 1,395-base-pair open reading frame, encoding a protein of 465 amino acids with moderate similarity to ubiquitin at the amino terminus and a RING-finger motif at the carboxy terminus. The gene spans more than 500 kilobases and has 12 exons, five of which (exons 3-7) are deleted in the patient. Four other AR-JP patients from three unrelated families have a deletion affecting exon 4 alone. A 4.5-kilobase transcript that is expressed in many human tissues but is abundant in the brain, including the substantia nigra, is shorter in brain tissue from one of the groups of exon-4-deleted patients. Mutations in the newly identified gene appear to be responsible for the pathogenesis of AR-JP, and we have therefore named the protein product 'Parkin'.

Adult↗
PubMed2001

Tbx1 haploinsufficieny in the DiGeorge syndrome region causes aortic arch defects in mice.

DiGeorge syndrome is characterized by cardiovascular, thymus and parathyroid defects and craniofacial anomalies, and is usually caused by a heterozygous deletion of chromosomal region 22q11.2 (del22q11) (ref. 1). A targeted, heterozygous deletion, named Df(16)1, encompassing around 1 megabase of the homologous region in mouse causes cardiovascular abnormalities characteristic of the human disease. Here we have used a combination of chromosome engineering and P1 artificial chromosome transgenesis to localize the haploinsufficient gene in the region, Tbx1. We show that Tbx1, a member of the T-box transcription factor family, is required for normal development of the pharyngeal arch arteries in a gene dosage-dependent manner. Deletion of one copy of Tbx1 affects the development of the fourth pharyngeal arch arteries, whereas homozygous mutation severely disrupts the pharyngeal arch artery system. Our data show that haploinsufficiency of Tbx1 is sufficient to generate at least one important component of the DiGeorge syndrome phenotype in mice, and demonstrate the suitability of the mouse for the genetic dissection of microdeletion syndromes.

Animals↗
PubMed1993

Isolation of a Miller-Dieker lissencephaly gene containing G protein beta-subunit-like repeats.

Lissencephaly (agyria-pachygyria) is a human brain malformation manifested by a smooth cerebral surface and abnormal neuronal migration. Identification of the gene(s) involved in this disorder would facilitate molecular dissection of normal events in brain development. Type 1 lissencephaly occurs either as an isolated abnormality or in association with dysmorphic facial appearance in patients with Miller-Dieker syndrome. About 15% of patients with isolated lissencephaly and more than 90% of patients with Miller-Dieker syndrome have microdeletions in a critical 350-kilobase region in chromosome 17p13.3 (ref. 6). These deletions are hemizygous, so haplo-insufficiency for a gene in this interval is implicated. Here we report the cloning of a gene (LIS-1, lissencephaly-1) in 17p13.3 that is deleted in Miller-Dieker patients. Non-overlapping deletions involving either the 5' or 3' end of the gene were found in two patients, identifying LIS-1 as the disease gene. The deduced amino-acid sequence shows significant homology to beta-subunits of heterotrimeric G proteins, suggesting that it could possibly be involved in a signal transduction pathway crucial for cerebral development.

Amino Acid Sequence↗
PubMed1995

Rubinstein-Taybi syndrome caused by mutations in the transcriptional co-activator CBP.

The Rubinstein-Taybi syndrome (RTS) is a well-defined syndrome with facial abnormalities, broad thumbs, broad big toes and mental retardation as the main clinical features. Many patients with RTS have been shown to have breakpoints in, and microdeletions of, chromosome 16p13.3 (refs 4-8). Here we report that all these breakpoints are restricted to a region that contains the gene for the human CREB binding protein (CBP), a nuclear protein participating as a co-activator in cyclic-AMP-regulated gene expression. We show that RTS results not only from gross chromosomal rearrangements of chromosome 16p, but also from point mutations in the CBP gene itself. Because the patients are heterozygous for the mutations, we propose that the loss of one functional copy of the CBP gene underlies the developmental abnormalities in RTS and possibly the propensity for malignancy.

Amino Acid Sequence↗