George Kitsos

A report on 10 new patients with heterozygous mutations in the COL11A1 gene and a review of genotype–phenotype correlations in type XI collagenopathies

A series of 44 unrelated patients in whom COL2A1 screening demonstrated normal results but whose phenotype was nevertheless highly suggestive of either Stickler syndrome (with ocular involvement) or Marshall syndrome were investigated for mutations in the COL11A1 gene. Heterozygous COL11A1 mutations were found in 10 individuals. A splice site alteration (involving introns 47–55) was present in seven cases, with one in intron 50 (c.3816 + 1G > A) occurring in three patients. Two patients had a different deletion, and a missense mutation (Gly1471Asp) was observed in one case. In 4/10 patients the phenotype was classified as Marshall syndrome because of early‐onset severe hearing loss and characteristic facial features. These four patients were all heterozygous for a splice site mutation in intron 50. One of these cases had a type 1 vitreous anomaly despite the presence of a COL11A1 mutation. The remaining 6/10 patients had an overlapping Marshall–Stickler phenotype with less pronounced facial features. None of these had a mutation in the hot spot region of intron 50.

Genetic linkage of autosomal dominant primary open angle glaucoma to chromosome 3q in a Greek pedigree

A locus for juvenile onset open angle glaucoma (OAG) has been assigned to chromosome 1q in families with autosomal dominant inheritance (GLC1A), due to mutations in the TIGR/MYOC gene. For adult onset OAG, called primary open angle glaucoma or POAG, five loci have so far been mapped to different chromosomes (GLC1B-GLC1F). Except for the GLC1B locus, the other POAG loci have so far been reported only in single large pedigrees. We studied a large family identified in Epirus, Greece, segregating POAG in an autosomal dominant fashion. Clinical findings included increased cup to disc ratio (mean 0.7), characteristic glaucomatous changes in the visual field, and intraocular pressure before treatment more than 21 mmHg (mean 31 mmHg), with age at diagnosis 33 years and older. Linkage analysis was performed between the disease phenotype and microsatellite DNA polymorphisms. Linkage was established with a group of DNA markers located on chromosome 3q, where the GLC1C locus has previously been described in one large Oregon pedigree. A maximal multipoint lod score of 3.88 was obtained at marker D3S1763 (penetrance 80%). This represents the second POAG family linked to the GLC1C locus on chromosome 3q, and haplotype analysis in the two families suggests an independent origin of the genetic defect.

The use of array-CGH in a cohort of Greek children with developmental delay

BackgroundThe genetic diagnosis of mental retardation (MR) is difficult to establish and at present many cases remain undiagnosed and unexplained. Standard karyotyping has been used as one of the routine techniques for the last decades. The implementation of Array Comparative Genomic Hybridization (array-CGH) has enabled the analysis of copy number variants (CNVs) with high resolution. Major cohort studies attribute 11% of patients with unexplained mental retardation to clinically significant CNVs. Here we report the use of array-CGH for the first time in a Greek cohort. A total of 82 children of Greek origin with mean age 4.9 years were analysed in the present study. Patients with visible cytogenetic abnormalities ascertained by standard karyotyping as well as those with subtelomeric abnormalities determined by Multiplex Ligation-dependent Probe Amplification (MLPA) or subtelomeric FISH had been excluded.ResultsFourteen CNVs were detected in the studied patients. In nine patients (11%) the chromosomal aberrations were inherited from one of the parents. One patients showed two duplications, a 550 kb duplication in 3p14.1 inherited from the father and a ~1.1 Mb duplication in (22)(q13.1q13.2) inherited from the mother. Although both parents were phenotypically normal, it cannot be excluded that the dual duplication is causative for the patients clinical profile including dysmorphic features and severe developmental delay. Furthermore, three de novo clinically significant CNVs were detected (3.7%). There was a ~6 Mb triplication of 18q21.1 in a girl 5 years of age with moderate MR and mild dysmorphic features and a ~4.8 Mb duplication at (10)(q11.1q11.21) in a 2 years old boy with severe MR, multiple congenital anomalies, severe central hypotonia, and ataxia. Finally, in a 3 year-old girl with microcephaly and severe hypotonia a deletion in (2)(q31.2q31.3) of about ~3.9 Mb was discovered. All CNVs were confirmed by Fluorescence in situ hybridization (FISH). For the remaining 9 patients the detected CNVs (inherited duplications or deletions of 80 kb to 800 kb in size) were probably not associated with the clinical findings.ConclusionsGenomic microarrays have within the recent years proven to be a highly useful tool in the investigation of unexplained MR. The cohorts reported so far agree on an around 11% diagnostic yield of clinically significant CNVs in patients with unexplained MR. Various publicly available databases have been created for the interpretation of identified CNVs and parents are analyzed in case a rare CNV is identified in the child. We have conducted a study of Greek patients with unexplained MR and confirmed the high diagnostic value of the previous studies. It is important that the technique becomes available also in less developed countries when the cost of consumables will be reduced.

Oxidative stress in dry age-related macular degeneration and exfoliation syndrome.

Abstract Oxidative stress refers to cellular or molecular damage caused by reactive oxygen species, which especially occurs in age-related conditions as a result of an imbalance between the production of reactive oxygen species and the antioxidant defense response. Dry age-related macular degeneration (AMD) and exfoliation syndrome (XFS) are two common and complex age-related conditions that can cause irreversible vision loss. Two subtypes of AMD, which is the leading cause of blindness in the Western world, exist: the most prevalent dry type and the most severe wet type. Early dry AMD is characterized by formation of drusen, which are sub-retinal deposits, in the macular area and may progress to geographic atrophy with more dramatic manifestation. XFS is a systemic disorder of the extracellular matrix characterized by the accumulation of elastic fibrils that leads, in most cases, to glaucoma development with progressive and irreversible vision loss. Due to the aging population, the prevalence of these already-widespread conditions is increasing and is resulting in significant economic and psychological costs for individuals and for society. The exact composition of the abnormal drusen and XFS material as well as the mechanisms responsible for their production and accumulation still remain elusive, and consequently treatment for both diseases is lacking. However, recent epidemiologic, genetic and molecular studies support a major role for oxidative stress in both dry AMD and XFS development. Understanding the early molecular events in their pathogenesis and the exact role of oxidative stress may provide novel opportunities for therapeutic intervention for the prevention of progression to advanced disease.

Biomarkers in primary open angle glaucoma

Abstract Glaucoma, a leading cause of blindness worldwide, is currently defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may lead to specific visual field defects over time. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP). Glaucoma can be divided roughly into two main categories, ‘open angle’ and ‘closed angle’ glaucoma. Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice loss of vision until the disease has progressed significantly. Primary open angle glaucoma (POAG) is described distinctly as a multifactorial optic neuropathy that is chronic and progressive with a characteristic acquired loss of optic nerve fibers. Such loss develops in the presence of open anterior chamber angles, characteristic visual field abnormalities, and IOP that is too high for the healthy eye. It manifests by cupping and atrophy of the optic disc, in the absence of other known causes of glaucomatous disease. Several biological markers have been implicated with the disease. The purpose of this study was to summarize the current knowledge regarding the non-genetic molecular markers which have been predicted to have an association with POAG but have not yet been validated.

Systematic review of the association between Alzheimer’s disease and chronic glaucoma

A potential association between Alzheimer’s disease (AD) and chronic glaucoma has been suggested but results of epidemiological studies have been inconsistent. Therefore, we performed a systematic review and critical appraisal of this literature. We searched systematically in PubMed from December 1964 to September 2013 and identified 239 articles potentially relevant for abstract and full-text review. Statistical heterogeneity (variability) across studies was evaluated using the Cochran Q test and the I2 statistic, and the Newcastle-Ottawa score was used to assess study quality. Ten studies were finally selected. Compared to non-demented participants, patients with AD had a statistically significant decreased risk of glaucoma but the results were very heterogeneous, and thus summary estimates were not reported (I2, 89%; Pheterogeneity, <0.001). The study results ranged from large positive relative risks identified in small and poorly-conducted studies to weak inverse associations or null estimates observed in some cohort and record-linkage studies, but the summary estimates were essentially driven by a large retrospective cohort using medical claims that may be afflicted by underdiagnosis bias. There was also evidence for substantial publication bias (Egger’s P≤0.01). The association of AD and glaucoma is heterogeneous and most studies are small and inadequately designed. Large prospective studies with long follow-ups are warranted to clarify this association.

Refining the primary open-angle glaucoma GLC1C region on chromosome 3 by haplotype analysis

The GLC1C locus for primary open‐angle glaucoma (POAG) is inherited as an autosomal dominant trait. This region on chromosome 3 is 11 cM long. DNA samples from members of a Greek and an American GLC1C family were obtained to determine whether additional typing of microsatellite markers in family members might narrow the region. GLC1C family members were evaluated clinically for POAG on the basis of open angles, intraocular pressures, cupping of discs, and visual fields. DNA samples from the Greek and Oregon GLC1C families were used to further refine the GLC1C region using microsatellite markers. A total of 22 affected members were identified in the two families. Common alleles for D3S3637 and D3S3612 were present in the disease haplotype from both families, suggesting that they may have a common founder. A newly diagnosed patient in the American family had a recombination in the distal portion of the GLC1C haplotype. This recombination narrows the GLC1C region from 11 to 4 cM.

Combined 22q11.1-q11.21 deletion with 15q11.2-q13.3 duplication identified by array-CGH in a 6 years old boy

BackgroundDeletions of chromosome 22q11 are present in over 90% of cases of DiGeorge or Velo-Cardio-Facial syndrome (DGS/VCFS). 15q11-q13 duplication is another recognized syndrome due to rearrangements of several genes, belonging to the category of imprinted genes. The phenotype of this syndrome varies but has been clearly associated with developmental delay and autistic spectrum disorders. Co-existence of the two syndromes has not been reported so far.ResultsHere we report a 6-year-old boy presenting growth retardation, dysmorphic features and who exhibited learning difficulties. Fluorescence in situ hybridization (FISH) analysis of the proband revealed a deletion of DiGeorge Syndrome critical region (TUPLE). Array-CGH analysis revealed an interstitial duplication of 12 Mb in size in the area 15q11.2-q13.3, combined with a 3.2 Mb deletion at region 22q11.1-q11.21. FISH analysis in the mother showed a cryptic balanced translocation between chromosome 15 and chromosome 22 (not evident by classic karyotyping).DiscusionThe clinical manifestations could be related to both syndromes and the importance of array-CGH analysis in cases of unexplained developmental delay is emphasized. The present case further demonstrates how molecular cytogenetic techniques applied in the parents were necessary for the genetic counseling of the family.

Detailed molecular and clinical investigation of a child with a partial deletion of chromosome 11 (Jacobsen syndrome)

BackgroundJacobsen syndrome (JBS) is a rare chromosomal disorder leading to multiple physical and mental impairment. This syndrome is caused by a partial deletion of chromosome 11, especially subband 11q24.1 has been proven to be involved. Clinical cases may easily escape diagnosis, however pancytopenia or thrombocytopenia may be indicative for JBS.ResultsWe report a 7.5 years old boy presenting with speech development delay, hearing impairment and abnormal platelet function. High resolution SNP oligonucleotide microarray analysis revealed a terminal deletion of 11.4 Mb in size, in the area 11q24.1-11qter. This specific deletion encompasses around 170 genes. Other molecular techniques such as fluorescence in situ hybridization and multiplex ligation-dependent probe amplification were used to confirm the array-result.DiscussionOur results suggest that the identification and detailed analysis of similar patients with abnormal platelet function and otherwise mild clinical features will contribute to identification of more patients with 11q deletion and JBS.

Deletion 2q31.2-q31.3 in a 4-year-old girl with microcephaly and severe mental retardation†

Deletion 2q31.2-q31.3 in a 4-Year-Old Girl With Microcephaly and Severe Mental Retardation Emmanouil Manolakos,* Annalisa Vetro, Konstantinos Kefalas, Loretta Thomaidis, Georgios Aperis, Sotirios Sotiriou, George Kitsos, Martina Merkas, Stavros Sifakis, Ioannis Papoulidis, Thomas Liehr, Orsetta Zuffardi, and Michael B. Petersen Bioiatriki S.A., Laboratory of Genetics, Athens, Greece Dipartimento di Patologia Umana ed Ereditaria, Universita di Pavia, Pavia, Italy Department of Paediatrics, University of Athens, Aglaia Kyriakou Children’s Hospital, Athens, Greece Nephrology Clinic, General Hospital Rhodes, Agioi Apostoloi, Rhodes, Greece Department of Embryology, University of Thessaly, Larissa, Greece Department of Ophthalmology, University of Ioannina, Ioannina, Greece Jena University Hospital, Institute of Human Genetics and Anthropology, Jena, Germany Department of Obstetrics and Gynecology, University Hospital of Heraklion, Crete, Greece Eurogenetica, Laboratory of Genetics, Athens, Greece Department of Genetics, Institute of Child Health, Athens, Greece