Biomedical subjects

Michael B Petersen

Publications and source records attributed to Michael B Petersen.

16 recordsLinked to original sources

PubMed2007

A seventh locus for otosclerosis, OTSC7, maps to chromosome 6q13-16.1.

Otosclerosis is a common form of hearing impairment among white adults with a prevalence of 0.3-0.4%. It is caused by abnormal bone homeostasis of the otic capsule that compromises free motion of the stapes in the oval window. Otosclerosis is in most patients a multifactorial disease, caused by both genetic and environmental factors. In some cases, the disease is inherited as a monogenic autosomal dominant trait, sometimes with reduced penetrance. However, families large enough for genetic linkage studies are extremely rare. To date, five loci (OTSC1-5) have been reported, but none of the responsible genes have been cloned yet. An additional locus, OTSC6, has been reported to the HUGO nomenclature committee but the relevant linkage study has not been published. In this study, a genome-wide linkage study was performed in a large Greek pedigree segregating autosomal dominant otosclerosis. A seventh locus, OTSC7, was localized on chromosome 6q13-16.1 with a multipoint LOD score of 7.5 in the 13.47 cM region defined by markers D6S1036 (centromeric) and D6S300 (telomeric). Linkage analysis of this new locus in 13 smaller Belgian and Dutch families has identified one family from The Netherlands in which allele segregation suggests linkage to this region. The overlap between the critical regions of these two families is a 1.06 Mb interval between the genetic markers D6S1036 (centromeric) and D6S406 (telomeric) on chromosome 6q13.

Chromosome Mapping↗

PubMed2006

Prenatal diagnosis of achondroplasia presenting with multiple-suture synostosis: a novel association.

OBJECTIVE: We report an atypical case of a fetus presenting with a combined achondroplasia and multiple craniosynostosis phenotype. METHODS: Sonographic monitoring in conjunction with molecular genetic analysis was performed in a 32-gestational weeks fetus. RESULTS: Sonographic findings were consistent with a diagnosis of achondroplasia associated with multiple-suture synostosis. The most common G380R FGFR3 achondroplasia mutation was detected. CONCLUSION: The most common achondroplasia mutation should be considered for prenatal DNA testing in cases with ultrasound findings of achondroplasia and multiple-suture synostosis. This is crucial for the genetic counselling and perinatal management of the fetus.

Achondroplasia↗

PubMed2006

Prenatal diagnosis of glycogen storage disease type IV.

BACKGROUND: Glycogen storage disease type IV (GSD-IV) is a rare autosomal recessive disorder due to mutations in the GBE1 gene causing deficiency of the glycogen branching enzyme (GBE). Prenatal diagnosis has occasionally been performed by the measurement of the GBE activity in cultured chorionic villi (CV) cells. METHODS: Two unrelated probands with severe hypotonia at birth and death during the neonatal period were diagnosed with GSD-IV on the basis of postmortem histological findings. DNA analysis revealed truncating GBE1 mutations in both families. RESULTS: Prenatal diagnosis was performed in subsequent pregnancies by determination of branching enzyme activity and DNA analysis of CV or cultured amniocytes. Detailed autopsies of the affected fetuses at 14 and 24 weeks of gestation demonstrated intracellular inclusions of abnormal glycogen characteristic of GSD-IV. CONCLUSION: Prenatal diagnosis of GSD-IV by DNA analysis is highly accurate in genetically confirmed cases.

1,4-alpha-Glucan Branching Enzyme↗

PubMed2006

A large GLC1C Greek family with a myocilin T377M mutation: inheritance and phenotypic variability.

PURPOSE: POAG is a complex disease; therefore, families in which a glaucoma gene has been mapped may carry additional POAG genes. The goal of this study was to determine whether mutations in the myocilin (MYOC) gene on chromosome 1 are present in two POAG families, which have previously been mapped to the GLC1C locus on chromosome 3. METHODS: The three exons of MYOC were screened by denaturing (d)HPLC. Samples with heteroduplex peaks were sequenced. Clinical findings were compared with genotype status in all available family members over the age of 20 years. RESULTS: A T377M coding sequence change in MYOC was identified in family members of the Greek GLC1C family but not in the Oregon GLC1C family. Individuals carrying both the MYOC T377M variant and the GLC1C haplotype were more severely affected at an earlier age than individuals with just one of the POAG genes, suggesting that these two genes interact or that both contribute to the POAG phenotype in a cumulative way.

Adult↗

PubMed2005

Monogenic nonsyndromic otosclerosis: audiological and linkage analysis in a large Greek pedigree.

OBJECTIVE: The aim of our study was to characterize the hearing impairment in a large multigenerational Greek family with autosomal dominant nonsyndromic otosclerosis and to perform genetic linkage analysis to known otosclerosis loci and collagen genes. In addition, we looked for mutations in the NOG gene to rule out congenital stapes ankylosis syndrome. METHODS: Audiological analysis of the affected persons was based on multiple linear regression (MLR) analysis and construction of age-related typical audiograms (ARTA). Genotyping of microsatellite DNA polymorphisms for known otosclerosis (OTSC) loci or collagen genes and linkage analysis using the MLINK computer program were performed. The coding region of the NOG gene was screened for mutations by direct DNA sequencing. RESULTS: The hearing loss in this family appears in childhood as conductive, but soon becomes mixed. Because the additional sensorineural component is progressive, this finally has lead to a pure sensorineural hearing loss in some family members, as the conductive component is masked. Audiological analysis showed an age-independent conductive component and a progressive frequency-specific sensorineural component. Linkage analysis excluded linkage to the four known otosclerosis loci (OTSC1, OTSC2, OTSC3, and OTSC5), as well as to the COL1A1 and COL1A2 genes. Mutation analysis of the coding region of the NOG gene did not reveal any disease causing mutation. CONCLUSIONS: This study represents the first description of a detailed audiological analysis in a large pedigree segregating otosclerosis as a monogenic autosomal dominant trait. Exclusion of the four known otosclerosis loci in this family shows that monogenic otosclerosis is a genetically heterogeneous disease involving at least five different genes. A mutation in the NOG gene is not the underlying molecular mechanism of the early onset otosclerosis segregating in this family.

Ankylosis↗

PubMed2005

Trisomy 13 due to rea(13q;13q) is caused by i(13) and not rob(13;13)(q10;q10) in the majority of cases.

We have used 20 PCR-based DNA polymorphisms to determine whether trisomy 13 due to de novo rea(13q;13q) in six cases is caused by translocation (13q;13q) or isochromosome (13q;13q); to determine the parental origin of the rearrangements and the mechanisms of formation. The six probands were three liveborn children with clinical features characteristic of Patau's syndrome and three fetuses diagnosed prenatally by amniocentesis or CVS. Five cases were isochromosomes with two identical q arms, one of maternal and four of paternal origin. Only one case was a Robertsonian translocation of maternal origin.

Chromosomes, Human, Pair 13↗

PubMed2005

Hellenic National Mutation database: a prototype database for mutations leading to inherited disorders in the Hellenic population.

The exponential discovery rate of new genomic alterations, leading to inherited disorders, as well as the need for comparative studies of different population's mutation frequencies necessitates recording their population-wide spectrum in online mutation databases. We report the construction of the Hellenic National Mutation database (http://www.goldenhelix.org/hellenic), a prototype database derived from a multicenter academic initiative, aiming to provide high quality and up-to-date information on the underlying genetic heterogeneity of inherited disorders found in the Hellenic population. Database records include informative summaries of the various genetic disorders studied in the Hellenic population, focused in particular on their incidence in Greece, a comprehensive reference list, and a well-structured query interface, which provides easy access to the list of the different mutations responsible for the inherited disorders in the Hellenic population. Also, extensive links to the respective Online Mendelian Inheritance in Man (OMIM) entries and, when available, to the locus-specific databases are provided, so that the user can retrieve the maximum amount of information from a single website. Furthermore, the Hellenic National Mutation database design allows easy data entry and curation. Creation of the Hellenic National Mutation database will significantly facilitate molecular diagnosis of inherited disorders in Greece and will motivate further investigation of yet unknown genetic diseases in the Hellenic population.

Computational Biology↗

PubMed2005

Different mechanisms preclude mutant CLDN14 proteins from forming tight junctions in vitro.

Mutations in claudin 14 (CLDN14) cause nonsyndromic DFNB29 deafness in humans. The analysis of a murine model indicated that this phenotype is associated with degeneration of hair cells, possibly due to cation overload. However, the mechanism linking these alterations to CLDN14 mutations is unknown. To investigate this mechanism, we compared the ability of wild-type and missense mutant CLDN14 to form tight junctions. Ectopic expression in L mouse fibroblasts (LM cells) of wild-type CLDN14 protein induced the formation of tight junctions, while both the c.254T>A (p.V85D) mutant, previously identified in a Pakistani family, and the c.301 G>A (p.G101R) mutant, identified in this study through the screen of 183 Spanish and Greek patients affected with sporadic nonsyndromic deafness, failed to form such junctions. However, the two mutant proteins differed in their ability to localize at the plasma membrane. We further identified hitherto undescribed exons of CLDN14 that are utilized in alternative spliced transcripts. We demonstrated that different mutations of CLDN14 impaired by different mechanisms the ability of the protein to form tight junctions. Our results indicate that the ability of CLDN14 to be recruited to these junctions is crucial for the hearing process.

Alternative Splicing↗

PubMed2005

3C syndrome with cryptorchidism and posterior embryotoxon.

We report a case of the 3C (cranio-cerebello-cardiac) syndrome, also known as Ritscher-Schinzel syndrome, a rare autosomal recessive disorder characterized by craniofacial, cerebellar, and cardiac anomalies. In addition to features previously reported the child had Wormian bones of the skull, intra-abdominal testes, and posterior embryotoxon that have not previously been reported as part of the 3C syndrome.

Abnormalities, Multiple↗

PubMed2004

DNA studies of mono- and pseudodicentric isochromosomes 18q.

The description of isochromosomes 18 has so far mainly been by cytogenetic studies and based on identical banding pattern of the two arms. However, only molecular techniques are capable to distinguish an isochromosome from a translocation, whole arm or reciprocal, between two chromosomes 18. We have used 23 PCR-based DNA polymorphisms to determine the parental origin and mechanisms of formation in four patients with isochromosomes 18q and to demonstrate that they were consistent with true isochromosomes. Three of the probands were liveborn children with clinical features characteristic of Edwards syndrome, one proband was a fetus diagnosed at prenatal diagnosis. In one case the isochromosome was monocentric with two identical q arms of maternal origin, formed by misdivision of the centromere and loss of p arm material. Another monocentric case had 47 chromosomes with isochromosomes i(18p) and i(18q) formed by maternal postzygotic centromeric misdivision and segregation of both isochromosomes, or by meiosis II centromeric misdivision and nondisjunction (without recombination in meiosis I). In two cases, the isochromosomes were dicentric with genetically identical arms composed of a part of the short and the whole long arm of chromosome 18 of paternal origin. The formation of the fused chromosomes can be explained by postzygotic exchange of sister chromatids on the short arm of chromosome 18, followed by breakage and U-shape reunion of sister chromatids.

Adult↗

PubMed2003

Double supernumerary isodicentric chromosomes derived from 15 resulting in partial hexasomy.

We report two unrelated patients each with two supernumerary marker chromosomes (SMCs) derived from chromosome 15, and thus resulting in partial hexasomy. Hexasomy in the one case (family 1) was diagnosed at prenatal diagnosis and did not include the Prader-Willi/Angelman critical region (PWACR). The double SMCs were also found in the mother, the pregnancy continued to term, and an apparently phenotypically normal child was born. This represents the first report of transmission of double SMCs from mother to child. In the second case (family 2), the hexasomy did include the PWACR and was de novo in origin. This patient manifested severe psychomotor retardation, clefting of the soft palate, hypotonia, seizure-like episodes, and other phenotypic features. The aberrant phenotype is attributable to the hexasomy for the PWACR gene loci. The normal homologs of chromosome 15 proved to be biparental in origin while the two SMCs appeared maternal.

Adult↗

PubMed2002

Prevalence of GJB2 mutations in prelingual deafness in the Greek population.

OBJECTIVE: Mutations in the gene encoding the gap junction protein connexin 26 (GJB2) have been shown as a major contributor to prelingual, sensorineural, nonsyndromic, recessive deafness. One specific mutation, 35delG, has accounted for the majority of the mutations detected in the GJB2 gene in Caucasian populations. The aim of our study was to determine the prevalence and spectrum of GJB2 mutations in prelingual deafness in the Greek population. METHODS: In a collaboration with the major referral centers for childhood deafness in Greece, patients were examined by an extensive questionnaire to exclude syndromic forms and environmental causes of deafness and by allele-specific polymerase chain reaction (PCR) for the detection of the 35delG mutation. Patients heterozygous for the 35delG mutation were further analyzed by direct genomic sequencing of the coding region of the GJB2 gene. RESULTS: The 35delG mutation was found in 42.2% of the chromosomes in 45 familial cases of prelingual, nonsyndromic deafness (18 homozygotes and 2 heterozygotes) and in 30.6% of the chromosomes in 165 sporadic cases (45 homozygotes and 11 heterozygotes). Direct genomic sequencing in heterozygous patients revealed the L90P (2 alleles), W24X (2 alleles), R184P (2 alleles), and 291insA (1 allele) mutations. CONCLUSION: Mutations in the GJB2 gene are responsible for about one third of prelingual, sensorineural, nonsyndromic deafness in the Greek population, and allele-specific PCR is an easy screening method for the common 35delG mutation.

Base Sequence↗

PubMed2002

Human CCS gene: genomic organization and exclusion as a candidate for amyotrophic lateral sclerosis (ALS).

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a progressive lethal disorder of large motor neurons of the spinal cord and brain. In approximately 20% of the familial and 2% of sporadic cases the disease is due to a defect in the gene encoding the cytosolic antioxidant enzyme Cu, Zn-superoxide dismutase (SOD1). The underlying molecular defect is known only in a very small portion of the remaining cases and therefore involvement of other genes is likely. As SOD1 receives copper, essential for its normal function, by the copper chaperone, CCS (Copper Chaperone for SOD), we considered CCS as a potential candidate gene for ALS. RESULTS: We have characterized the genomic organization of CCS and determined exon-intron boundaries. The 823 bp coding region of the CCS is organized in 8 exons. We have evaluated involvement of the CCS in ALS by sequencing the entire coding region for mutations in 20 sporadic ALS patients. CONCLUSIONS: No causative mutations for the ALS have been detected in the CCS gene in 20 sporadic ALS patients analyzed, but an intragenic single nucleotide polymorphism has been identified.

Aged↗

PubMed2002

Maternal uniparental isodisomy 20 in a foetus with trisomy 20 mosaicism: clinical, cytogenetic and molecular analysis.

The clinical significance of trisomy 20 mosaicism detected prenatally remains uncertain due to the rarity of liveborn cases with inconsistent clinical findings, and lack of long-term follow-up and outcome. We describe a case of true trisomy 20 mosaicism in a liveborn girl with maternal uniparental isodisomy of chromosome 20 in the diploid blood cells. Trisomy 20 mosaicism was originally detected in amniotic fluid (98%) and was confirmed in the term placenta (100%), as well as in the blood (10%) and urine sediment (100%) of the neonate. There was intrauterine and postnatal growth retardation, but otherwise the newborn manifested no gross abnormalities. At 9 months of age moderate psychomotor retardation, central hypotonia with peripheral hypertonia, numerous minor morphogenetic variants, marked kyphosis, and extensive Mongolian spot were observed. To our knowledge this represents the first case of trisomy 20 mosaicism detected prenatally and confirmed in different tissues of the newborn, where uniparental disomy was demonstrated in the diploid cell line. The clinical and laboratory findings in our patient are compared with those of five previously reported cases of UPD20, suggesting that maternal UPD20 might be associated with a characteristic phenotype.

Chromosomes, Human, Pair 20↗

PubMed2001

Mutations in the TMPRSS3 gene are a rare cause of childhood nonsyndromic deafness in Caucasian patients.

Two loci for nonsyndromic recessive deafness located on chromosome 21q22.3 have previously been reported, DFNB8 and DFNB10. Recently a gene which encodes a transmembrane serine protease, TMPRSS3 or ECHOS1, was found to be responsible for both the DFNB8 and DFNB10 phenotypes. To determine the contribution of TMPRSS3 mutations in the general congenital/childhood nonsyndromic deaf population we performed mutation analysis of the TMPRSS3 gene in 448 unrelated deaf patients from Spain, Italy, Greece, and Australia who did not have the common 35delG GJB2 mutation. From the 896 chromosomes studied we identified two novel pathogenic mutations accounting for four mutant alleles and at least 16 nonpathogenic sequence variants. The pathogenic mutations were a 1-bp deletion resulting in a frameshift and an amino acid substitution in the LDLRA domain of TMPRSS3. From this and another study we estimate the frequency of TMPRSS3 mutations in our sample as 0.45%, and approximately 0.38% in the general Caucasian childhood deaf population. However, TMPRSS3 is still an important contributor to genetic deafness in populations with large consanguineous families.

Amino Acid Sequence↗

PubMedDate not supplied

Prenatal diagnosis of trisomy 2 mosaicism: a case report.

We report a case of trisomy 2 mosaicism detected upon amniocentesis in a woman with advanced maternal age. A mos 47,XY,+2(4)/46,XY(21) karyotype was revealed using standard GTG banding. There were no pathological sonographic findings and the fetal size was normal for gestational age at 16th week. The use of serial high-resolution ultrasound examination of the fetus to detect major abnormalities was offered as an option to the parents who, however, decided for termination of the pregnancy. Fetal autopsy did not reveal any malformations. Trisomy 2 mosaicism is associated with variable phenotypic abnormalities without a specific pattern, intrauterine growth restriction, fetal demise or stillbirth. The rarity of trisomy-2 mosaicism in prenatal diagnosis, as well as the increased risk of an abnormal outcome makes the diagnostic approach and genetic counseling difficult.

Adult↗