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At least 793 records · Page 44Linked to original sources
PubMed2001

Somatic INK4a-ARF locus mutations: a significant mechanism of gene inactivation in squamous cell carcinomas of the head and neck.

The INK4a-ARF locus is located on human chromosome 9p21 and is known to encode two functionally distinct tumor-suppressor genes. The p16(INK4a) (p16) tumor-suppressor gene product is a negative regulator of cyclin-dependent kinases 4 and 6, which in turn positively regulate progression of mammalian cells through the cell cycle. The p14(ARF) tumor-suppressor gene product specifically interacts with human double minute 2, leading to the subsequent stabilization of p53 and G(1) arrest. Previous investigations analyzing the p16 gene in squamous cell carcinomas of the head and neck (SCCHNs) have suggested the predominate inactivating events to be homozygous gene deletions and hypermethylation of the p16 promoter. Somatic mutational inactivation of p16 has been reported to be low (0-10%, with a combined incidence of 25 of 279, or 9%) and to play only a minor role in the development of SCCHN. The present study examined whether this particular mechanism of INK4a/ARF inactivation, specifically somatic mutation, has been underestimated in SCCHN by determining the mutational status of the p16 and p14(ARF) genes in 100 primary SCCHNs with the use of polymerase chain reaction technology and a highly sensitive, nonradioactive modification of single-stranded conformational polymorphism (SSCP) analysis termed "cold" SSCP. Exons 1alpha, 1beta, and 2 of INK4a/ARF were amplified using intron-based primers or a combination of intron- and exon-based primers. A total of 27 SCCHNs (27%) exhibited sequence alterations in this locus, 22 (22%) of which were somatic sequence alterations and five (5%) of which were a single polymorphism in codon 148. Of the 22 somatic alterations, 20 (91%) directly or indirectly involved exon 2, and two (9%) were located within exon 1alpha. No mutations were found in exon 1beta. All 22 somatic mutations would be expected to yield altered p16 proteins, but only 15 of them should affect p14(ARF) proteins. Specific somatic alterations included microdeletions or insertions (nine of 22, 41%), a microrearrangement (one of 22, 5%), and single nucleotide substitutions (12 of 22, 56%). In addition, we analyzed the functional characteristics of seven unique mutant p16 proteins identified in this study by assessing their ability to inhibit cyclin-dependent kinase 4 activity. Six of the seven mutant proteins tested exhibited reduced function compared with wild-type p16, ranging from minor decreases of function (twofold to eightfold) in four samples to total loss of function (29- to 38-fold decrease) in two other samples. Overall, somatic mutation of the INK4a/ARF tumor suppressor locus, resulting in functionally deficient p16 and possibly p14(ARF) proteins, seems to be a prevalent event in the development of SCCHN. Mol. Carcinog. 30:26-36, 2001.

Base Sequence↗
PubMed2000

Williams syndrome: cognition, personality, and adaptive behavior.

Williams syndrome is caused by a microdeletion of at least 16 genes on chromosome 7q11.23. The syndrome results in mild to moderate mental retardation or learning disability. The behavioral phenotype for Williams syndrome is characterized by a distinctive cognitive profile and an unusual personality profile. Relative to overall level of intellectual ability, individuals with Williams syndrome typically show a clear strength in auditory rote memory, a strength in language, and an extreme weakness in visuospatial construction. The personality of individuals with Williams syndrome involves high sociability, overfriendliness, and empathy, with an undercurrent of anxiety related to social situations. The adaptive behavior profile for Williams syndrome involves clear strength in socialization skills (especially interpersonal skills related to initiating social interaction), strength in communication, and clear weakness in daily living skills and motor skills, relative to overall level of adaptive behavior functioning. Literature relevant to each of the components of the Williams syndrome behavioral phenotype is reviewed, including operationalizations of the Williams syndrome cognitive profile and the Williams syndrome personality profile. The sensitivity and specificity of these profiles for Williams syndrome, relative to individuals with other syndromes or mental retardation or borderline normal intelligence of unknown etiology, is considered. The adaptive behavior profile is discussed in relation to the cognitive and personality profiles. The importance of operationalizations of crucial components of the behavioral phenotype for the study of genotype/phenotype correlations in Williams syndrome is stressed. MRDD Research Reviews 2000;6:148-158.

Adaptation, Psychological↗
PubMed1998

Imprinted genes in the Prader-Willi deletion.

Parent-of-origin-specific deletions of proximal chromosome 15q cause either the Prader-Willi syndrome (paternal deletion) or the Angelman syndrome (maternal deletion), two distinct neurodevelopmental disorders. In contrast to the Angelman syndrome, which can also be caused by mutations in a single gene (UBE3A, encoding a ubiquitin ligase), the Prader-Willi syndrome is caused by deletions in about two-thirds of cases and by maternal uniparental disomy in the remaining third. The consequence of both mechanisms, in addition to rare microdeletions or so-called 'imprinting mutations', is lack of the products of multiple genes in the region that are normally expressed only from the paternal chromosome. One gene that is consistently silent in the Prader-Willi syndrome is SNRPN, which encodes the small nuclear ribonucleoprotein particle-associated polypeptide N that forms part of the spliceosomes in the brain. A systematic search for other imprinted genes in the Prader-Willi syndrome region revealed a paternally expressed transcript (IPW, for imprinted in the Prader-Willi region) and a similarly imprinted mouse homologue (Ipw) in the conserved syntenic region on mouse chromosome 7. Ipw is highly expressed in the brain and alternatively spliced to generate different transcripts. Since there is no open reading frame that is conserved in the human and mouse IPW genes, they are postulated to function as untranslated RNAs, possibly regulating transcription in cis in the region.

Animals↗
PubMed2002

Deletion of RBM and DAZ in azoospermia: evaluation by PRINS.

Molecular and cytogenetic studies from infertile men have shown that one or more genes controlling spermatogenesis are located in proximal Yq11.2 in interval 6 of the Y chromosome. Microdeletions within the azoospermia factor region (AZF) are often associated with azoospermia and severe oligospermia in men with idiopathic infertility. We evaluated cells from a normal-appearing 27-year-old man with infertility and initial karyotype of 45,der(X)t(X;Y)(p22.3;p11.2)[8]/46,t(X;Y)(p22.3;p11.2)[12]. By fluorescence in situ hybridization with dual-color whole chromosome paint probes for X and Y chromosomes, we confirmed the Xp-Yp interchange. By primed in situ labeling, we identified translocation of the SRY gene from its original location on Yp to the patient's X chromosome at band Xp22. We also obtained evidence that the apparent marker was a der(Y) (possibly a ring) containing X and Y domains, and observed that the patient's genome was deleted for RBM and DAZ, two candidate genes for AZF.

Adult↗
PubMed2002

Further delineation of the chromosome 14q terminal deletion syndrome.

A patient with hypotonia, blepharophimosis, ptosis, a bulbous nose, a long philtrum, upturned corners of the mouth, and mild developmental delay was found to have a small subtelomeric deletion of the long arm of chromosome 14 (q32.31-qter). In comparing her phenotype with previously reported patients with similar 14q deletions, due to either a linear deletion or to a ring chromosome 14, a clinically recognizable terminal 14q microdeletion syndrome was evident. Due to the limited number of cases reported, it was not possible to assign specific features to specific regions of terminal 14q. The comparison of features in cases with a linear deletion of 14qter (n = 19) to those in cases with a deletion due to a ring chromosome 14 (n = 23), both with the same breakpoint in 14q, showed that seizures and retinitis pigmentosa have been found only in patients with ring chromosomes. Several hypotheses are put forward to explain this difference: mitotic instability of ring chromosomes; a telomere position effect in ring chromosomes in which the 14p telomere silences nearby gene(s) on the q-arm; and dose-dependent gene(s) involved in seizures and retinitis pigmentosa located on the short arm of chromosome 14. In our opinion, only seizures may be explained by the mitotic instability of ring chromosomes, while both seizures and retinitis pigmentosa may be explained by silencing of gene(s) on 14q by the 14p telomere; the third hypothesis seems unlikely to explain either symptom.

Abnormalities, Multiple↗
PubMed2002

Further case of Cantú syndrome: exclusion of cryptic subtelomeric chromosome aberrations.

Cantú syndrome consists of hypertrichosis, osteochondrodysplasia, and cardiomegaly, and has been reported in 18 patients to date. We report an infant with Cantú syndrome. In addition to typical findings, he had relatively mild radiological and cardiological manifestations. Previously undescribed findings included pyloric stenosis and elevated alkaline phosphatase levels. Brain scans showed bilateral calcification of the Arteriae thalamostriatae and widening of the outer liquor spaces and lateral ventricles. Because the propositus is the youngest patient reported to date, our findings refine the clinical spectrum of Cantú syndrome in neonates and young infants. The etiology and mode of inheritance of Cantú syndrome are unknown. Most cases are sporadic. Microdeletions have been discussed as a possible cause of Cantú syndrome. Recently, several syndromes with multiple congenital anomalies and mental retardation have been shown to be caused by subtelomeric chromosome aberrations. We excluded the presence of a cryptic subtelomeric chromosome anomaly in our patient by fluorescence in situ hybridization (FISH) screening with locus-specific probes.

Abnormalities, Multiple↗
PubMed2002

Partial deletions of the long arm of chromosome 13 associated with holoprosencephaly and the Dandy-Walker malformation.

Two patients with partial deletions of the long arm of chromosome 13, del(13)(13q21-q34) and del(13)(13q22-q33), respectively, multiple congenital anomalies including holoprosencephaly (HPE) and the Dandy-Walker malformation (DWM) are described. The occurrence of HPE and the DWM in both of these patients suggests that, in addition to ZIC2, which is important for normal development of the forebrain, there is at least one other dosage-sensitive gene in 13q22-q33 that plays an important role in brain development. The DWM is anatomically and developmentally distinct from HPE. The presence of a DWM in each of these two patients with partial deletions of the long arm of chromosome 13 suggests that haploinsufficiency at a locus in 13q22-q33 may cause this anomaly. These findings suggest that microdeletions in 13q22-q33 may be found in a proportion of patients with an apparently isolated DWM. Therefore, careful high-resolution cytogenetic analysis (550 band level or greater) of 13q22-q33 may be considered in these patients. Furthermore, future molecular studies of this region may reveal candidate gene loci for the DWM.

Chromosome Deletion↗
PubMed2002

Teebi hypertelorism syndrome: report of a family with previously unrecognized findings.

We present a family consisting of a mother, a daughter, and a son with Teebi hypertelorism syndrome, including some previously unrecognized manifestations. The clinical findings include a prominent forehead, arched eyebrows, pronounced hypertelorism, long philtrum, mild interdigital webbing, fifth-finger clinodactyly, umbilical anomalies, and hypotonia. The mother and daughter also had ptosis requiring surgical correction. The daughter has bilateral iridochorioretinal colobomas with high hyperopia and a small umbilical hernia. The son has less striking facial features but was born with a small omphalocele, large ASD secundum, PDA, bilateral cryptorchidism right hydronephrosis, and a cystic left kidney. The mother had an umbilical hernia requiring surgical correction as a child and a history of heart murmur. Both children have normal hearing and mild developmental delay. Their high-resolution karyotypes were normal and the FISH for 22q11 microdeletion was negative in the daughter. We conclude that cardiac defects in Teebi hypertelorism syndrome are not rare findings and that eye colobomas and renal anomalies were previously unrecognized.

Abnormalities, Multiple↗
PubMed2001

Misclassification risk of patients with bilateral cleft lip and palate and manifestations of median facial dysplasia: A new variant of del(22q11.2) syndrome?

The generic term median facial dysplasia (MFD) describes a subgroup of patients with cleft lip and palate exhibiting characteristic craniofacial defects: (1) short prolabium, (2) absence of frenulum labii, (3) hypoplasia of premaxilla, (4) absent upper central and lateral incisors of the cleft side, and (5) deficient septal cartilage and nasal spine. Gross brain malformations are usually absent in MFD. The same craniofacial malformations are also described in patients with holoprosencephaly sequence (HPE-S). We report on two male patients with bilateral cleft lip and palate showing the facial findings of MFD or HPE-S. Additional congenital malformations were anal atresia in one patient and severe cardiac defect in the other. In both, HPE was excluded by brain imaging, although uncommon brain anomalies were detected consisting of multiple white-matter lesions in the one patient and unusual enlargement and tortuosity of intracerebral blood vessels in both patients. In addition to facial anomalies, the patients also had psychiatric problems typically seen in velo-cardio-facial syndrome (VCFS). Fluorescence in situ hybridization (FISH) analysis confirmed a 22q11.2 microdeletion in both.

Abnormalities, Multiple↗
PubMed2001

Angelman syndrome: mimicking conditions and phenotypes.

The diagnosis of Angelman syndrome (AS) can be confirmed by genetic laboratory in about 80% of cases. In 20%, the diagnosis remains clinical, but often there is uncertainty about the correctness of the clinical diagnosis and alternative diagnoses may be investigated. In evaluating individuals for AS in our center since 1989, we have encountered several mimicking conditions, and additional ones have been reported in the literature. Mimicking conditions can be grouped into the areas of chromosome, single gene, and symptom complex anomalies. Microdeletions or microduplications include chromosome regions 2,4,17, 22, and 15. Single gene conditions include methylene tetrahydrofolate reductase deficiency (MTHFR), Rett syndrome, alpha-thalassemia retardation syndrome (ATR-X), and Gurrieri syndrome. Symptom complexes include cerebral palsy, static encephalopathy, Lennox-Gastaut syndrome, autism spectrum disorder, pervasive developmental delay (PDD), and mitochondrial disorders. We present a review of these mimicking disorders to increase the awareness about conditions that can lead to an incorrect clinical diagnosis of AS.

Angelman Syndrome↗
PubMed1988

Complex glycerol kinase deficiency: molecular-genetic, cytogenetic, and clinical studies of five Japanese patients.

Five male Japanese patients with complex glycerol kinase deficiency (CGKD) and their relatives were studied clinically, cytogenetically, and molecular-genetically. All patients had muscular dystrophy or muscle weakness, mental retardation, congenital adrenal hypoplasia, and glycerol kinase deficiency. High-resolution GTG-banded chromosomes showed a microdeletion in the Xp21 region in all four patients examined and in all five mothers. Southern hybridizations, after digestions by restriction endonucleases, with various cloned DNAs (D2, 99-6, B24, C7, L1-4, cDMD13-14, J66-HI, P20, J-Bir, ERT87-30, ERT87-15, ERT87-8, ERT87-1, XJ-1.1, 754, cx5.7, and OTC-1) that are located around Xp21 also showed a deletion in the genome of all patients and mothers. Although the deletion differed in size among patients, a segment commonly absent was located between the genomic sequences corresponding to L1-4 and cDMD13-14. This finding indicated that the gene coding for glycerol kinase (GK) is located within this segment. A comparison of the clinical manifestations of the present five patients and reported CGKD or Duchenne muscular dystrophy (DMD) patients with DNA deletion suggests the existence of a certain gene responsible for gonadotropin deficiency (GTD). The result of the present study and results of previous studies suggest that genes for ornithine transcarbamylase (OTC), DMD, and GK and putative genes responsible for congenital adrenal hypoplasia (AHC) and GTD are arranged from telomere to centromere as pter--GTD--AHC--GK--DMD--OTC--cen.

Adolescent↗
PubMed1990

Cytogenetic and molecular study of Angelman syndrome.

Six patients, including two sibs, with Angelman syndrome (AS; three females and three males, aged 11 to 18 years) were studied cytogenetically. Molecular analysis was also performed. Using high-resolution banding technique, we detected a microdeletion in the proximal region of chromosome 15q in four cases. The deleted segment was heterogenous between these patients, and the common deleted region appeared to be 15q11.2. Four patients with deleted 15q were all sporadic cases, whereas in the sib cases we could not detect a visible deletion in the long arm of chromosome 15. However, there was no clinical difference between sporadic cases and sib cases. Densitometric analysis of autoradiographic bands of Southern hybridization using two DNA segments, pML34 and pTD3-21, as probes demonstrated that two patients had only one copy for each of the probes. In the remaining four patients, including the sibs, two copies of each sequence were retained. The probes used here detect a molecular deletion in most Prader-Willi syndrome patients. Thus the segment causing AS is localized adjacent to the critical segment of Prader-Willi syndrome. There seemed to be heterogeneity for the molecular deletion within AS individuals.

Adolescent↗
PubMed1990

Chromosome evolution and high-resolution analysis of leucocytes, bone marrow, and tumor cells of retinoblastoma patients.

High-resolution cytogenetics were applied to leucocytes, bone marrow, and tumors of 8 retinoblastoma (Rb) patients in search of microdeletions or subtle rearrangements and in order to determine clonal evolution. Four of 9 tumors (Rb1, Rb6.1, Rb6.2, and Rb8) showed a deletion in the characteristic region on 13q while 2 others (Rb3 and Rb4) were hemizygous for chromosome 13 in approximately one-third of the cells. Our study presents a particularly high incidence of chromosome 13 anomalies as compared to the previously published data. Furthermore, comparison of karyotypes of 3 significant cases (Rb1, Rb6, and Rb8) allows the reconstruction of the necessary steps in the evolution of retinoblastoma. It also shows the need for a double mutation in tumor development, both in hereditary and non-hereditary cases. High-resolution chromosome analysis of retinoblastoma patients provides a rare opportunity to study the succession of events necessary for tumor development.

Bone Marrow↗
PubMed1991

Aicardi syndrome: early neuroradiological manifestations and results of DNA studies in one patient.

A patient with Aicardi syndrome is presented. We report results of DNA analysis from the patient and her parents with probes mapped to Xp21.3-22.3 in an attempt to localize a deletion in this region. No signs of a microdeletion could be detected, using 5 different DNA markers. Further, it is suggested that a specific combination of cerebral abnormalities may be characteristic of the syndrome and that antenatal ultrasonographic diagnosis may be feasible.

Agenesis of Corpus Callosum↗
PubMed1991

Pseudo-trisomy 13 syndrome.

We have coined the term "pseudo-trisomy 13 syndrome" to designate cases of holoprosencephaly, severe facial anomalies, postaxial polydactyly, various other congenital defects, and normal chromosomes. Eleven instances are summarized. Two pairs of sibs and two other cases with consanguinity suggest autosomal recessive inheritance. Autosomal recessive inheritance is possible. Alternately, an undetected microdeletion and etiologic heterogeneity (some cases possibly representing dominant new mutations) must be considered. Further delineation is necessary. It is hoped that this paper will serve as a focus for further discussion of the problem.

Abnormalities, Multiple↗
PubMed1993

Hypomandibular faciocranial dysostosis: another case and review.

We report on a third case of hypomandibular faciocranial dysostosis and review the literature. Manifestations include craniosynostosis, prominent eyes, deficient midface and zygomatic arches, short nose with anteverted nares, protruding lower face, minute oral aperture, persistent buccopharyngeal membrane, and severe mandibular hypoplasia. In contrast to coronal synostosis found in the 2 earlier cases, our patient had multiple sutural synostosis. The 2 affected sibs reported earlier suggest the possibility of autosomal recessive inheritance. However, gonadal mosaicism for a dominant mutation or an undetected microdeletion must also be considered at this early stage in the delineation of this disorder.

Abnormalities, Multiple↗
PubMed1993

DiGeorge anomaly with renal agenesis in infants of mothers with diabetes.

We report on 2 infants with the DiGeorge anomaly born to diabetic mothers treated with insulin. Both infants had unilateral renal agenesis. One of the mothers has manifestations suggestive of velo-cardio-facial syndrome (VCFS). Cytogenetic studies on both patients and the mother with apparent VCFS were normal. Molecular studies utilizing probes from the DiGeorge critical region did not demonstrate a 22q11 microdeletion in either patient or the mother with apparent VCFS. We conclude that maternal diabetes is a pathogenetic factor in the DiGeorge anomaly, and infants of diabetic mothers who have this anomaly should also be screened for renal agenesis.

Adult↗