Patient with three euchromatic supernumerary marker chromosomes derived from chromosomes 1, 12, and 18: characterization and evaluation of the aberrations.

The genetic relevance of small supernumerary marker chromosomes (sSMCs) depends on their content of euchromatin. In case of mosaicism, the phenotype of the carrier furthermore is influenced by the distribution of the marker in the body. In the majority of reported cases no correlation of the degree of mosaicism in the tissue(s) analyzed and the phenotype could be detected. In particular, non-acrocentric derived sSMCs show a strong tendency to appear in mosaic state irrespective of the clinical picture. We present a patient with cognitive disability and mild craniofacial dysmorphisms with mosaicism of three different autosomal marker chromosomes. The extra chromosomes were analyzed by a combination of SNP array and a variety of fluorescence in situ hybridization (FISH) probes. All three markers were identified as ring chromosomes containing different amounts of euchromatic material derived from chromosome 1 (1p12 → q21), 12 (12p13.1 → q13.11) and 18 (18p11.21 → q11.2). The size and the frequency of the sSMCs were strikingly different, besides, we observed an unequal combination of the three derivates.

Analysis of SYCP3 encoding synaptonemal complex protein 3 in human aneuploidies.

OBJECTIVES: To test the hypothesis that mutations of SYCP3 encoding synaptonemal complex protein 3, result in increased frequency of aneuploidies in humans. METHODS: Mutation analysis of the PCR-amplified 8 coding exons and exon-intron boundaries of the SYCP3 gene was done by direct sequencing of DNA isolated from 35 aneuploid fetuses of women having a potentially increased likelihood for an underlying genetic predisposition for chromosomal non-disjunction. RESULTS: Based on the results of conventional karyotyping, the 35 aneuploid fetuses of 33 women were divided into separate groups: 9 aneuploid conceptuses of couples with recurrent aneuploid conceptions (4 of the women 35 years or younger), 12 conceptuses with double/multiple aneuploidies (5 of the women 35 years or younger), and 14 conceptuses with single aneuploidies of women younger than 35 years (8 trisomies and 6 monosomies). No pathogenic mutations in the SYCP3 coding exons and the immediately flanking intronic sequences were found. CONCLUSIONS: Under the assumption that genetic predisposition for chromosomal non-disjunction leading to aneuploidy is most likely polygenic in nature, our data suggest that SYCP3 mutations are not one of the common causes in humans.

A phenotype map for 14q32.3 terminal deletions.

Detailed molecular-cytogenetic studies combined with thorough clinical characterization are needed to establish genotype-phenotype correlations for specific chromosome deletion syndromes. Although many patients with subtelomeric deletions have been reported, the phenotype maps for many of the corresponding syndromes, including the terminal deletion 14q syndrome, are only slowly emerging. Here, we report on five patients with terminal partial monosomy of 14q32.3 and characteristic features of terminal deletion 14q syndrome. Four of the patients carry de novo terminal deletions of 14q, three of which have not yet been reported. One patient carries an unbalanced translocation der(14)t(9;14)(q34.3;q32.3). Minimum deletion sizes as determined by molecular karyotyping and FISH are 5.82, 5.56, 4.17, 3.54, and 3.29 Mb, respectively. Based on our findings and a comprehensive review of the literature, we refine the phenotype map for typical clinical findings of the terminal deletion 14q syndrome (i.e., intellectual disability/developmental delay, muscular hypotonia, postnatal growth retardation, microcephaly, congenital heart defects, genitourinary malformations, ocular coloboma, and several dysmorphic signs). Combining this phenotype map with benign copy-number variation data available from the Database of Genomic Variants, we propose a small region critical for certain features of the terminal deletion 14q syndrome which contains only seven RefSeq genes.

Duplication 3q13.11q23: Longitudinal study in a patient over a period of more than 7 years and refinements of the breakpoints.

In 2006, we reported the first case with a pure duplication of proximal 3q. In these rare aberrations, detailed clinical and developmental investigations at different ages are required to provide sufficient phenotypic documentation. Clinical and psychological differences were therefore regularly documented in our case. Supplemental genetic investigations comprised conventional karyotyping, fluorescence in-situ hybridization, single nucleotide polymorphism array analysis, and microsatellite typing. Thus, the exact position and extension of the duplication (3q13.11q23), the size (35.6 Mb), and the paternal origin could be determined. The development of our patient was followed up in detail over a period of 7.5 yr and thus enabled specific characterization of the phenotype of the patient.

Genetic counseling in Robertsonian translocations der(13;14): frequencies of reproductive outcomes and infertility in 101 pedigrees.

Robertsonian translocations 13/14 are the most common chromosome rearrangements in humans. However, most studies aimed at determining risk figures are more than 20 years old. Their results are often contradictory regarding important topics in genetic counseling such as infertility and unfavorable pregnancy outcomes. Here, we present a study on a sample of 101 previously unreported pedigrees of der(13;14)(q10;q10). In order to minimize problems of partial ascertainment, we included families with a wide range of reasons of ascertainment such as birth of a child with congenital anomalies, prenatal diagnosis due to maternal age, fertility problems and recurrent pregnancy loss. No evidence of increased infertility rates of female and male carriers was found. The detected miscarriage frequency of female carriers was higher than previously reported (27.6 +/- 4.0% of all spontaneous pregnancies). This may be explained by an over-correction of earlier studies, which excluded all unkaryotyped miscarriages. In three out of 42 amniocenteses, translocation trisomies 13 were diagnosed (7.1 +/- 4.0% of all amniocenteses). The frequency of stillbirths was 3.3 +/- 1.6% for female carriers and 1.4 +/- 1.4% for male carriers. A low risk for the live birth of translocation trisomy 13 children was confirmed since no live born children with trisomy 13 or Pätau syndrome were detected in the ascertainment-corrected sample.

Rare interstitial deletion 9q31.2 to q33.1 de novo: longitudinal study in a patient over a period of more than 20 years.

The female carrier of a de novo interstitial deletion 9q [karyotype 46,XX,del(9)(q31.2q33.1)] was followed up over a period of more than 20 years. She shows facial dysmorphisms and significant growth retardation. Motor abilities are restricted by muscular hypotonia and malposition of the feet. She has mental retardation. There was no speech development and phases of autism were reported. By analyses with FISH and short tandem repeat markers, the interstitial deletion was confirmed and characterized to span 9q31.2q33.1, comprising at least 7.07 Mb. The aberration is of paternal origin.

First report of a partial trisomy 3q12-q23 de novo--FISH breakpoint determination and phenotypic characterization.

We present a 1-year-old boy with mild mental retardation, postnatal growth retardation, and facial dysmorphisms such as frontal bossing, laterally accentuated bushy eyebrows, deep set eyes with long lashes, hypertelorism, and a broad nasal bridge. Except for hip dysplasia, no congenital malformations were detected. By conventional cytogenetics a derivative chromosome 3 de novo was diagnosed which was identified as tandem dup(3)(q12q23) by fluorescence in situ hybridization (FISH) applying arm specific paints and eight different YAC-probes. The duplicated segment lies proximally from the reported dup(3q) syndrome critical region, thus explaining the absence of characteristic phenotypic features of dup(3q) syndrome. To our knowledge this is the first report of a patient with pure trisomy of this proximal region of the long arm of chromosome 3.

Further delineation of the phenotype maps for partial trisomy 16q24 and Jacobsen syndrome by a subtle familial translocation t(11;16)(q24.2;q24.1).

We report on two cases of distal monosomy 11q and partial trisomy 16q due to a familial subtle translocation detected by FISH subtelomere screening. Exact breakpoint analyses by FISH with panels of BAC probes demonstrated a 9.3-9.5 megabase partial monosomy of 11q24.2-qter and a 4.9-5.4 megabase partial trisomy of 16q24.1-qter. The index patient displayed craniofacial dysmorphisms, mild mental retardation and postnatal growth retardation, muscular hypotonia, mild periventricular leukodystrophy, patent ductus arteriosus, thrombocytopenia, recurrent infections, inguinal hernia, cryptorchidism, pes equinovarus, and hearing deficiencies. In his mother's cousin who bears the identical unbalanced translocation, mild mental retardation, patent ductus arteriosus, hypogammaglobulinemia, recurrent infections, unilateral kidney hypoplasia, pes equinovarus, and hearing deficiencies were reported. Since only four descriptions of cryptic or subtle partial trisomies 16q have been published to date, our patients contribute greatly to the delineation of the phenotype of this genomic imbalance. In contrast to this, terminal deletions of the long arm of chromosome 11 cause a haploinsufficiency disorder (Jacobsen syndrome) in which karyotype-phenotype correlations are already being established. Here, our findings contribute to the refinement of a phenotype map for several Jacobsen syndrome features including abnormal brain imaging, renal malformations, thrombocytopenia/pancytopenia, inguinal hernia, testicular ectopy, pes equinovarus, and hearing deficiency.

Mosaic tetrasomy 14pter-q13 due to a supernumerary isodicentric derivate of proximal chromosome 14q.

Tetrasomy of proximal 14q is an extremely rare condition and has never been reported to be associated with survival. We here report on the first case of mosaic tetrasomy of 14pter-q13 due to a de-novo supernumerary pseudoisodicentric chromosome in a 2-year-old boy with multiple dysmorphisms and malformations. The marker was detectable in nearly 25% of lymphocytes as well as in cells from buccal mucosa. Detailed fluorescence in situ hybridization (FISH) analyses allowed the characterization of the marker to entirely consist of proximal 14q material and to be symmetric. The pattern of clinical features in our patient only slightly correspond to that of patients with trisomy of proximal 14q, but further cases are needed to define whether tetrasomy of proximal 14q is a separate entity.

New trends in chromosomal investigation in children with cardiovascular malformations.

We investigated a group of 376 children, seen over a period of 7 years with different types of congenital cardiovascular defects, to assess the presence of chromosomal aberrations. The diagnostic approach, achieved in 3 consecutive steps, revealed conventional chromosomal aberrations in 30 of the patients (8%) excluding trisomies 13, 18, 21. Fluorescence in situ hybridisation for microdeletions showed 51 microdeletions (15%), with 43 patients having deletions of 22q11.2, 7 patients with deletion of 7q11.23, and 1 patient with deletion of 4p16.3. In 23 patients with additional clinical abnormalities, we carried out a subtelomeric screening. This revealed, in two cases (9%), different subtelomeric aberrations, namely deletions of 1p and of 1q. Thus, subtelomeric screening proved to be a very valuable as a new diagnostic approach. Our approach to genetic investigation in three phases makes it possible to detect a high rate of pathologic karyotypes in patients with congenital cardiovascular malformations, thus guaranteeing more effective genetic counselling of the families, and a more precise prognosis for the patient.

Comprehensive analysis of human subtelomeres with combined binary ratio labelling fluorescence in situ hybridisation.

Cryptic subtelomeric chromosome rearrangements play an important role in the aetiology of mental retardation, congenital anomalies, miscarriages and neoplasia. To facilitate a comprehensive molecular-cytogenetic analysis of these extremely gene-rich and mutation-prone chromosome regions, novel multicolour fluorescence in situ hybridisation (FISH) techniques are being developed. As yet, subtelomeric FISH methods have either had limited multiplicities, making it necessary to perform many hybridisations per patient, or a limited scope of analysable chromosome mutation types, thus not detecting some aberration types such as pericentric inversions or very small aberrations. COBRA (COmbined Binary RAtio) labelling is a generic multicolour FISH technique that combines ratio and combinatorial labelling to attain especially high multiplicities with few fluorochromes. The Subtelomere COBRA FISH method ("S-COBRA FISH") described here detects efficiently all 41 BAC and PAC FISH probes necessary for a complete subtelomere screening in only two hybridisations. It was applied to the analysis of 10 cases with known and partially known aberrations and successfully detected balanced and unbalanced translocations, deletions and an unbalanced pericentric inversion in a mosaic situation. The ability of S-COBRA FISH to efficiently detect all types of balanced and unbalanced subtelomeric chromosome aberrations makes it the most comprehensive diagnostic procedure for human subtelomeric chromosome regions described to date.

Clinical, cytogenetic, and molecular findings in 45,X/47,XX,+18 mosaicism: clinical report and review of the literature.

We report cytogenetic and molecular findings performed in a patient with double mosaic aneuploidy. Chromosome analysis of amniotic fluid cells from a 17-week-old fetus was performed because of advanced maternal age. Two karyotypes were detected: 45,X and 47,XX,+18 (50:50%). The same cell lines were determined in uncultured and cultured amniocytes of a second amniotic fluid sample, in fetal lymphocytes, and in uncultured and cultured cells of achilles tendon by conventional cytogenetics and fluorescence in situ hybridization (FISH). In the different investigated tissues, the percentage of cells with 45,X karyotype ranged from 20-99% and the percentage of cells with 47,XX,+18 ranged from 1-80%. The pregnancy was terminated at 22 + 0 weeks because of a severe cardiac malformation. Pathologic examination showed a fetus with aspects typical for manifestation of trisomy 18 and monosomy X, especially in the internal organs. The parent and cell stage of origin was determined by short tandem repeat typing and revealed a maternal meiotic division error that led to trisomy 18, as well as a somatic loss of a paternal sex chromosome. Only two other patients with the same mosaicism have been reported so far. Genetic counseling and prognosis remains challenging.