High resolution Chromosomal Microarray Analysis (CMA) enhances the genetic profile of pediatric B-cell Acute Lymphoblastic Leukemia patients

Acute Lymphoblastic Leukemia (ALL) is a malignancy of the immature lymphoid cells mainly associated with numerical and structural chromosomal aberrations. The current standard for profiling the diverse genetic background comprises a combination of conventional karyotype and FISH analysis for the most common translocations, albeit with many limitations. Chromosomal Microarray Analysis (CMA) is a high throughput whole genome method that is gradually implemented in routine clinical practice, but not many studies have compared the two methods. Here we aim to investigate the added benefits of utilizing the high resolution 2 x 400 K G3 CGH + SNP CMA platform in routine diagnostics of pediatric ALL. From the 29 bone marrow samples that were analyzed, CMA identified clinically relevant findings in 83%, while detecting chromosomal aberrations in 75% of the patients with normal conventional karyotype. The most common finding was hyperdiploidy (20%), and the most common submicroscopic aberration involved CDKN2A/B genes. The smallest aberration detected was a 9 kb partial NF1 gene duplication. The prognosis of the patients when combining conventional cytogenetics and CMA was either changed or enhanced in 66% of the cases. A rare duplication possibly indicative of a cryptic ABL1-NUP214 fusion gene was found in one patient. We conclude that CMA, when combined with conventional cytogenetic analysis, can significantly enhance the genetic profiling of patients with pediatric ALL in a routine clinical setting.

Position effect, cryptic complexity, and direct gene disruption as disease mechanisms in de novo apparently balanced translocation cases

The majority of apparently balanced translocation (ABT) carriers are phenotypically normal. However, several mechanisms were proposed to underlie phenotypes in affected ABT cases. In the current study, whole-genome mate-pair sequencing (WG-MPS) followed by Sanger sequencing was applied to further characterize de novo ABTs in three affected individuals. WG-MPS precisely mapped all ABT breakpoints and revealed three possible underlying molecular mechanisms. Firstly, in a t(X;1) carrier with hearing loss, a highly skewed X-inactivation pattern was observed and the der(X) breakpoint mapped ~87kb upstream an X-linked deafness gene namely POU3F4, thus suggesting an underlying long-range position effect mechanism. Secondly, cryptic complexity and a chromothripsis rearrangement was identified in a t(6;7;8;12) carrier with intellectual disability. Two translocations and a heterozygous deletion disrupted SOX5; a dominant nervous system development gene previously reported in similar patients. Finally, a direct gene disruption mechanism was proposed in a t(4;9) carrier with dysmorphic facial features and speech delay. In this case, the der(9) breakpoint directly disrupted NFIB, a gene involved in lung maturation and development of the pons with important functions in main speech processes. To conclude, in contrast to familial ABT cases with identical rearrangements and discordant phenotypes, where translocations are considered coincidental, translocations seem to be associated with phenotype presentation in affected de novo ABT cases. In addition, this study highlights the importance of investigating both coding and non-coding regions to decipher the underlying pathogenic mechanisms in these patients, and supports the potential introduction of low coverage WG-MPS in the clinical investigation of de novo ABTs.

A boy with conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), borderline intellectual disability, and 47,XXY syndrome in combination with a 7q11.23 duplication, 11p15.5 deletion, and 20q13.33 deletion

BACKGROUND

This is a case with multiple chromosomal aberrations which are likely etiological for the observed psychiatric phenotype consisting of attention deficit hyperactivity and conduct disorders.

CASE PRESENTATION

We report on an 11 year-old boy, admitted to the pediatric hospital for behavioral difficulties and a delayed neurodevelopmental trajectory. A cytogenetic analysis and high-resolution microarray comparative genomic hybridization (CGH) analysis was performed. The cytogenetic analysis revealed 47,XYY syndrome, while CGH analysis revealed an additional duplication and two deletions. The 7q11.23 duplication is associated with speech and language delay and behavioral symptoms, a 20q13.33 deletion is associated with autism and early onset schizophrenia and the 11p15.5 microdeletion is associated with developmental delay, autism, and epilepsy. The patient underwent a psychiatric history, physical examination, laboratory testing, and a detailed cognitive, psychiatric, and occupational therapy evaluation which are reported here in detail.

CONCLUSIONS

In the case of psychiatric patients presenting with complex genetic aberrations and additional psychosocial problems, traditional psychiatric and psychological approaches can lead to significantly improved functioning. Genetic diagnostic testing can be highly informative in the diagnostic process and may be applied to patients in psychiatry in case of complex clinical presentations.

Recurrent copy number variations as risk factors for autism spectrum disorders: analysis of the clinical implications

Chromosomal microarray analysis (CMA) is currently considered a first-tier diagnostic assay for the investigation of autism spectrum disorders (ASD), developmental delay and intellectual disability of unknown etiology. High-resolution arrays were utilized for the identification of copy number variations (CNVs) in 195 ASD patients of Greek origin (126 males, 69 females). CMA resulted in the detection of 65 CNVs, excluding the known polymorphic copy number polymorphisms also found in the Database of Genomic Variants, for 51/195 patients (26.1%). Parental DNA testing in 20/51 patients revealed that 17 CNVs were de novo, 6 paternal and 3 of maternal origin. The majority of the 65 CNVs were deletions (66.1%), of which 5 on the X-chromosome while the duplications, of which 7 on the X-chromosome, were rarer (22/65, 33.8%). Fifty-one CNVs from a total of 65, reported for our cohort of ASD patients, were of diagnostic significance and well described in the literature while 14 CNVs (8 losses, 6 gains) were characterized as variants of unknown significance and need further investigation. Among the 51 patients, 39 carried one CNV, 10 carried two CNVs and 2 carried three CNVs. The use of CMA, its clinical validity and utility was assessed.

TAF1 Variants Are Associated with Dysmorphic Features, Intellectual Disability, and Neurological Manifestations

We describe an X-linked genetic syndrome associated with mutations in TAF1 and manifesting with global developmental delay, intellectual disability (ID), characteristic facial dysmorphology, generalized hypotonia, and variable neurologic features, all in male individuals. Simultaneous studies using diverse strategies led to the identification of nine families with overlapping clinical presentations and affected by de novo or maternally inherited single-nucleotide changes. Two additional families harboring large duplications involving TAF1 were also found to share phenotypic overlap with the probands harboring single-nucleotide changes, but they also demonstrated a severe neurodegeneration phenotype. Functional analysis with RNA-seq for one of the families suggested that the phenotype is associated with downregulation of a set of genes notably enriched with genes regulated by E-box proteins. In addition, knockdown and mutant studies of this gene in zebrafish have shown a quantifiable, albeit small, effect on a neuronal phenotype. Our results suggest that mutations in TAF1 play a critical role in the development of this X-linked ID syndrome.

Single-cell high resolution melting analysis: A novel, generic, pre-implantation genetic diagnosis (PGD) method applied to cystic fibrosis (HRMA CF-PGD)

BACKGROUND

Institutions offering CF-PGD face the challenge of developing and optimizing single cell genotyping protocols that should cover for the extremely heterogeneous CF mutation spectrum. Here we report the development and successful clinical application of a generic CF-PGD protocol to facilitate direct detection of any CFTR nucleotide variation(s) by HRMA and simultaneous confirmation of diagnosis through haplotype analysis.

METHODS

A multiplex PCR was optimized supporting co-amplification of any CFTR exon-region, along with 6 closely linked STRs. Single cell genotypes were established through HRM analysis following melting of the 2nd round PCR products and were confirmed by STR haplotype analysis of the 1st PCR products. The protocol was validated pre-clinically, by testing 208 single lymphocytes, isolated from whole blood samples from 4 validation family trios. Fifteen PGD cycles were performed and 103 embryos were biopsied.

RESULTS

In 15 clinical PGD cycles, genotypes were achieved in 88/93 (94.6%) embryo biopsy samples, of which 57/88 (64.8%) were deemed genetically suitable for embryo transfer. Amplification failed at all loci for 10/103 blastomeres biopsied from poor quality embryos. Six clinical pregnancies were achieved (2 twin, 4 singletons). PGD genotypes were confirmed following conventional amniocentesis or chorionic villus sampling in all achieved pregnancies.

CONCLUSIONS

The single cell HRMA CF-PGD protocol described herein is a flexible, generic, low cost and robust genotyping method, which facilitates the analysis of any CFTR genotype combination. Single-cell HRMA can be beneficial to other clinical settings, for example the detection of single nucleotide variants in single cells derived from clinical tumor samples.

Dysmorphology services: a snapshot of current practices and a vision for the future

Dysmorphology concerns the recognition and management of rare, multiple anomaly syndromes. Genomic technologies and software for gestalt recognition will re-shape dysmorphology services. In order to reflect on a model of the service in the post-genomic era, we compared the utility of dysmorphology consultations in two Mediterranean cities, Athens, Greece and Afula, Israel (MDS), the Manchester Centre for Genomic Medicine, a UK service with dysmorphology expertise (UKDS) and the DYSCERNE, digital service (DDS). We show that it is more likely that chromosome microarray analysis will be performed if suggested in the UKDS rather than in the MDS; this, most probably reflects the difference of access to genetic testing following funding limitations in the MDS. We also show that in terms of achieved diagnosis, the first visit to a dysmorphology clinic is more significant than a follow-up. We show that a confirmed syndrome diagnosis significantly decreases the requests for other, non-genetic, laboratory investigations. Conversely, it increases the requests for reviews by other specialists and, most significantly (t-test: 8.244), it increases further requests for screening for possible associated complications. This is the first demonstration of the demands, on a health service, following the diagnosis of a dysmorphic condition.

Psychomotor development of children born after preimplantation genetic diagnosis and parental stress evaluation

BACKGROUND

The increasing number of children conceived following preimplantation genetic diagnosis (PGD) necessitates the evaluation of their motor and cognitive development. The primary study objective was to evaluate the physical, developmental, and neurological outcome of children born after PGD in Greece. In addition, the secondary study objective was to compare the stress levels regarding parental roles between parents of PGD children and those of naturally conceived children.

METHODS

A cross-sectional study design was applied. The study population consisted of 31 children (aged 2 months to 7.5 years) born after PGD analysis and their parents. The developmental evaluation of children included a detailed physical evaluation and cognitive assessment with the Bayley Scales of Infant Development. The parent stress index was applied to evaluate comparative parental stress levels between those parents of PGD children and those of naturally conceived healthy children.

RESULTS

High rates of caesarean deliveries, increased incidence of prematurity, multiples and low-birth weight were observed among the 31 PGD children. Overall, 24 of the 31 PGD children had cognitive skills within normal range [general developmental quotient (GDQ): 86-115], while 6 children had lower levels of cognitive skills (GDQ<85). With regard to parental stress, PGD parents reported lower levels of parenting stress as compared to parents of naturally conceived children (P<0.01).

CONCLUSIONS

The enhanced frequency of poor cognitive and motor skills as well as low parental stress necessitates early detection and intervention for developmental delays among PGD children.

Sertoli cell tumor and gonadoblastoma in an untreated 29-year-old 46,XY phenotypic male with Frasier syndrome carrying a WT1 IVS9+4C>T mutation

OBJECTIVE

Frasier syndrome (FS) phenotype in 46,XY patients usually consists of female external genitalia, gonadal dysgenesis, high risk of gonadoblastoma and the development of end stage renal failure usually in the second decade of life. FS is caused by heterozygous de novo intronic splice site mutations of the Wilms' tumor suppressor gene 1 (WT1), although a few cases with typical exonic WT1 Denys-Drash mutations that resemble an FS phenotype have been described. The aim of this study was to present further data on the spectrum of FS phenotypes through the evaluation of a 29-year-old patient with a predominantly male phenotype and coexistence of Sertoli cell tumor and gonadoblastoma.

RESULTS

Genetic analysis using standard methods for DNA sequencing confirmed FS due to a WT1 gene mutation, IVS9+4C>T.

CONCLUSIONS

This very rare case illustrates the natural course of FS over many years due to the neglect by the patient to address his need for follow-up, while adding further data on the spectrum of FS phenotypes associated with IVS9+4 C>T mutations. The coexistence of the rare Sertoli cell tumor and gonadoblastoma emphasizes that early clinical recognition and molecular identification facilitates appropriate patient management, especially with respect to the high risk of gonadal malignancy.

An unusual case of Cat-Eye syndrome phenotype and extragonadal mature teratoma: review of the literature

BACKGROUND Cat-Eye syndrome (CES) with teratoma has not been previously reported. We present the clinical and molecular findings of a 9-month-old girl with features of CES and also a palpable midline neck mass proved to be an extragonadal mature teratoma, additionally characterized by array comparative genomic hybridization (aCGH). RESULTS High resolution oligonucleotide-based aCGH confirmed that the supernumerary marker chromosome (SMC) derived from chromosome 22, as was indicated by molecular cytogenetic analysis with fluorescence in situ hybridization (FISH). Additionally, aCGH clarified the size, breakpoints, and gene content of the duplication (dup 22q11.1q11.21; size:1.6 Mb; breakpoints: 15,438,946-17,041,773; hg18). The teratoma tissue was also tested with aCGH, in which the CES duplication was not found, but the analysis revealed three aberrations: del Xp22.3 (108,864-2788,689; 2.7 Mb hg18), dup Yp11.2 (6688,491-7340,982; 0.65 Mb, hg18), and dup Yq11.2q11.23 (12,570,853-27,177,133; 14.61 Mb, hg18). These results indicated 46 XY (male) karyotype of the teratoma tissue, making this the second report of mature extragonadal teratoma in a female neonate, probably deriving from an included dizygotic twin of opposite sex (fetus in fetu). CONCLUSIONS Our findings extend the phenotypic spectrum of CES syndrome, a disorder with clinical variability, pointing out specific dosage-sensitive genes that might contribute to specific phenotypic features.

MECP2 mutations and clinical correlations in Greek children with Rett syndrome and associated neurodevelopmental disorders

BACKGROUND

Mutations in the MECP2 gene (methyl-CpG-binding protein-2) are responsible for 60-95% of cases of Rett syndrome (RTT), an X-linked dominant neurodevelopmental disorder affecting mostly girls. Classic RTT is characterized by normal early development followed by psychomotor regression and onset of microcephaly, although variant forms are also observed. MECP2 has also been implicated in variable mental retardation (MR) phenotypes, including X-linked Mental Retardation (XLMR), Fragile-X-like Syndrome (FXS) and Angelman-like (AS) phenotypes.

AIM

The aim of the study was: (a) to evaluate the incidence and spectrum of MECP2 mutations in children with RTT and variant MR; (b) to evaluate phenotype-genotype correlations.

METHODS

Exons 3-4 were analyzed for mutations in 281 MR patients (aged 13 months-27 years old, 144 males-137 females) consisting of 88 patients referred for RTT and 193 patients referred for AS-like and FXS-like types of MR. Statistical analysis included correlation between classic MECP2-positive and MECP2-negative and variant RTT patients, and frequency of MECP2 mutations in the various categories.

RESULTS

Mutations were detected in ≈ 70% of classic and ≈ 21% of variant RTT, respectively. Amongst MR cases, 2.1% carried MECP2 mutations. MECP2-positive females had more problems in ambulation, muscle tone, tremor and ataxia, respiratory disturbances, head growth, hand use and stereotypies. Classic RTT-positive versus negative had significant respiratory and sitting problems and versus variant RTT-positive females ambulatory, hand and stereotypies problems.

CONCLUSION

The analysis of the MECP2 gene could provide a diagnostic tool for RTT and non-specific MR research.

Familial Pelizaeus-Merzbacher disease caused by a 320.6-kb Xq22.2 duplication and the pathological findings of a male fetus

BACKGROUND

Pelizaeus-Merzbacher disease (PMD) is a recessive, X-linked leukoencephalopathy attributed to impaired myelination during central nervous system development, caused by defects in the proteolipid protein 1 (PLP1) gene. PMD presents clinical variability, ranging from the severe connatal form to the classic form.

CASES

We report the clinical and molecular findings of two affected males, three carrier females, and an aborted male fetus with familial PMD. The two male probands presented with severe PMD phenotype and intellectual disability. High-resolution oligonucleotide-based array comparative genomic hybridization (aCGH) identified an Xq22.2 duplication of 320.6 kb (102641391-102961998, hg18), including the PLP1 gene and surrounding chromosomal region. Postmortem examination of the aborted fetus at 25 weeks' gestation showed focal subcortical white matter degeneration, focal gliosis, and cerebellar atrophy.

CONCLUSIONS

Genotype-phenotype correlation is provided. In the connatal form of PMD, leukodystrophy and cerebellar atrophy can occur antenatally and be established at 25 weeks' gestation. The observation of degenerative brain lesions occurring before the onset of subcortical myelination suggests that the PLP1 gene has a more complex role in human brain development, exceeding its structural function in myelin formation.

Phenotypic spectrum of 80 Greek patients referred as Noonan syndrome and PTPN11 mutation analysis: the value of initial clinical assessment

Noonan syndrome (NS) is a common multiple congenital anomaly entity, the diagnosis of which, on clinical grounds, is based on a comprehensive scoring system in order to select patients for molecular confirmation. Our aim was to evaluate the phenotypic characteristics in the light of PTPN11 mutations. The study revealed 80 patients who were referred with initial indication of NS or Noonan-like syndrome (NLS) and further assessed by a clinical geneticist; 60/80 index patients, mean age 5.9 ± 5.3 years, fulfilled the NS criteria. Molecular analysis of PTPN11 gene (exons and their flanking regions) of the total population revealed mutations in 17/80 patients, all belonging in the group of the patients screened with the scoring system. All mutations were heterozygous missense changes, mostly clustering in exon 3 (8/17), followed by exons 13 (3/17), 8 (2/17), 7 (2/17), 2 (1/17) and 4 (1/17). We conclude that (a) most of our clinically diagnosed NS cases were sporadic (b) PTPN11 analysis should be limited to those fulfilling the relevant NS criteria (c) Cardiovascular evaluation should comprise all NS patients, while pulmonary stenosis, short stature, and thorax deformities prevailed among those with PTPN11 mutations.

Microdeletion and microduplication 17q21.31 plus an additional CNV, in patients with intellectual disability, identified by array-CGH

The recognition of the 17q21.31 microdeletion and microduplication syndrome has been facilitated by high resolution oligonucleotide array comparative genome hybridization technology (aCGH). Molecular analysis of the 17q21.31 microdeletion/duplication syndrome demonstrated a critical region involving at least six genes, including STH and MAPT. The 17q21.31 microdeletion syndrome has an incidence of 1 in 16,000 births, while the microduplication 17q21.31 has been reported so far in only five patients. In general, phenotypes associated with 17q21.31 microduplication seem to be milder than those associated with the microdeletion. Here, we present four patients who have been referred for genetic evaluation by clinical geneticists due to developmental delay and minor congenital abnormalities. Previous standard karyotypes were negative, while aCGH analysis revealed three patients with 17q21.31 microdeletion and one with the respective microduplication, being the sixth reported case so far. Most importantly one of the microdeletion cases involves only partial MAPT gene deletion while leaving the STH gene intact. Two of our patients, one with the 17q21.31 microdeletion and another with the respective microduplication, carried additional clinically relevant microdeletions (del Xq21.31 and del 15q11.2, respectively), possibly modifying their phenotype.

Clinical and molecular description of a fetus in prenatal diagnosis with a rare de novo ring 10 and deletions of 12.59 Mb in 10p15.3-p14 and 4.22 Mb in 10q26.3

Ring chromosomes are rare cytogenetic findings and are mostly associated with an abnormal phenotype. We report on the prenatal diagnosis of a ring chromosome 10 in a fetus in which talipes equinovarus was incidentally found during routine obstetric ultrasound at 22 weeks of gestation. Amniocentesis was undertaken and cytogenetic analysis revealed a de novo non-mosaic apparently stable ring chromosome 10 replacing one of the two homologs. Multiplex Ligation-dependent Probe Amplification (MLPA) revealed subtelomeric deletions in both the short and long arm of chromosome 10. Analysis with high resolution micro-array based comparative genomic hybridization (array-CGH), defined the ring chromosome as del 10p15.3-p14 (12.59 Mb in size) and del 10q26.3 (4.22 Mb in size) and revealed the genes that are deleted. After elected termination of the pregnancy at 27th week of gestation a detailed autopsy of the fetus allowed for genotype-phenotype correlations. To our knowledge, this is the first case of a de novo ring chromosome 10 which is reported during prenatal diagnosis and is thoroughly investigated with array CGH and autopsy study.

FoSTeS, MMBIR and NAHR at the human proximal Xp region and the mechanisms of human Xq isochromosome formation

The recently described DNA replication-based mechanisms of fork stalling and template switching (FoSTeS) and microhomology-mediated break-induced replication (MMBIR) were previously shown to catalyze complex exonic, genic and genomic rearrangements. By analyzing a large number of isochromosomes of the long arm of chromosome X (i(Xq)), using whole-genome tiling path array comparative genomic hybridization (aCGH), ultra-high resolution targeted aCGH and sequencing, we provide evidence that the FoSTeS and MMBIR mechanisms can generate large-scale gross chromosomal rearrangements leading to the deletion and duplication of entire chromosome arms, thus suggesting an important role for DNA replication-based mechanisms in both the development of genomic disorders and cancer. Furthermore, we elucidate the mechanisms of dicentric i(Xq) (idic(Xq)) formation and show that most idic(Xq) chromosomes result from non-allelic homologous recombination between palindromic low copy repeats and highly homologous palindromic LINE elements. We also show that non-recurrent-breakpoint idic(Xq) chromosomes have microhomology-associated breakpoint junctions and are likely catalyzed by microhomology-mediated replication-dependent recombination mechanisms such as FoSTeS and MMBIR. Finally, we stress the role of the proximal Xp region as a chromosomal rearrangement hotspot.

De novo interstitial duplication of the 15q11.2-q14 PWS/AS region of maternal origin: Clinical description, array CGH analysis, and review of the literature

The 15q11-q13 PWS/AS critical region involves genes that are characterized by genomic imprinting. Multiple repeat elements within the region mediate rearrangements, including interstitial duplications, interstitial triplications, and supernumerary isodicentric marker chromosomes, as well as the deletions that cause Prader-Willi syndrome (PWS) and Angelman syndrome (AS). Recently, duplications of maternal origin concerning the same critical region have been implicated in autism spectrum disorders (ASD). We present a 6-month-old girl carrying a de novo duplication of maternal origin of the 15q11.2-q14 PWS/AS region (17.73 Mb in size) [46,XX,dup(15)(q11.2-q14)] detected with a high-resolution microarray-based comparative genomic hybridization (array-CGH). The patient is characterized by severe hypotonia, obesity, microstomia, long eyelashes, hirsutism, microretrognathia, short nose, severe psychomotor retardation, and multiple episodes of drug-resistant epileptic seizures, while her brain magnetic resonance imaging (MRI) documented partial corpus callosum dysplasia. In our patient the duplicated region is quite large extending beyond the Prader-Willi-Angelman critical region (PWACR), containing a number of genes that have been shown to be involved in ASD, exhibiting a severe phenotype, beyond the typical PWS/AS clinical manifestations. Reporting of similar well-characterized clinical cases with clearly delineated breakpoints of the duplicated region will clarify the contribution of specific genes to the phenotype.

Characterization of 23 small supernumerary marker chromosomes detected at pre-natal diagnosis: The value of fluorescence in situ hybridization

Small supernumerary marker chromosomes (sSMCs) cannot be identified or characterized unambiguously by conventional cytogenetic banding techniques. Until recently, the large variety of marker chromosomes, as well as the limitations in their identification, have presented a diagnostic problem. In order to determine the origin of sSMCs, we used a variety of fluorescence in situ hybridization (FISH) methods, including centromere-specific multicolor FISH, acrocentric specific multicolor FISH, subcentromere-specific multicolor FISH and multicolor FISH with whole chromosome paint probes. Moreover, uniparental disomy testing was in all cases attempted. From a total of 28,000 pre-natal samples from four diagnostic genetics laboratories in Greece, 23 (0.082%) supernumerary marker chromosomes were detected. The mean maternal age was 36.2 years (range 27-43) and the mean gestational age at which amniocentesis was performed was 18.5 weeks (range 16-23). Eighteen markers were de novo and 5 markers were inherited. Molecular cytogenetic methods were applied to determine the chromosomal origin and composition of the sSMC. In total, 17 markers were derived from acrocentric chromosomes (14, 15, 21 and 22) and 6 markers were non-acrocentric, derived from chromosomes 9, 16, 18, 20 and Y. Uniparental disomy was not detected in any of the cases studied. With regard to pregnancy outcome, 13 pregnancies resulted in normal healthy neonates, while 10 pregnancies were terminated due to ultrasound abnormalities. A total of 23 marker chromosomes from 28,000 pre-natal samples (0.082%) were identified. Molecular cytogenetic techniques provided valuable information on the chromosomal origin and composition of all the sSMCs. Especially in cases with normal ultrasound, the FISH results rendered genetic counseling possible in a category of cases previously considered a diagnostic problem. Abnormal outcome was observed in 10 cases (43,5%), 7 of which showed abnormal ultrasound findings. New technologies, such as array-comparative genomic hybridization, should be used in future genotype-phenotype correlation studies, although the high mosaicism rate poses a problem.

Milroy's primary congenital lymphedema in a male infant and review of the literature

Milroy's primary congenital lymphedema is a non-syndromic primary lymphedema caused mainly by autosomal dominant mutations in the FLT4 (VEGFR3) gene. Here, we report on a 6-month-old boy with congenital non-syndromic bilateral lymphedema at both feet and tibias, who underwent molecular investigation, consisted of PCR amplification and DHPLC analysis of exons 17-26 of the FLT4 gene. The clinical diagnosis of Milroy disease was confirmed by molecular analysis showing the c.3109G>C mutation in the FLT4 gene, inherited from the asymptomatic father. This is a known missense mutation, which substitutes an aspartic acid into a histidine on amino acid position 1037 of the resulting protein (p.D1037H), described in two other families with Milroy disease. A thorough genetic molecular investigation and clinical evaluation contributes to the provision of proper genetic counseling for parents of an affected child with Milroy disease. The herein described case, which is the third reported so far with c.3109G>C mutation, adds data on genotypic-phenotypic correlation of Milroy disease. The relative literature regarding the pathophysiology, molecular basis, clinical spectrum and treatment of Milroy disease is reviewed.

Phenotypic and genotypic variability in four males with MECP2 gene sequence aberrations including a novel deletion

The MECP2 gene mutations cause Rett syndrome (RTT) (OMIM: 312750), an X-linked dominant disorder primarily affecting girls. Until RTT was considered lethal in males, although now approximately 60 cases have been reported. Males with MECP2 mutations present with a broad spectrum of phenotypes ranging from neonatal encephalopathy to nonsyndromic mental retardation (MR). Four boys (aged, 3-11 y) were evaluated for MR. Patient 1 had autistic features. Patients 2 and 3 were brothers both presenting with psychomotor delay. Patient 4 showed dysmorphic features and behavioral problems reminiscent of FXS. All patients had a normal 46, XY karyotype and three were tested for FXS with negative results. MECP2 gene analysis of exons 3 and 4 was performed using methods based on the PCR, including Enzymatic Cleavage Mismatched Analysis (ECMA) and direct sequencing. Patient 1 presented somatic mosaicism for the classic RTT p.R106W mutation and patient 4 carried the p.T203M polymorphism. Analysis of the mothers in both cases revealed normal DNA sequences. Patients 2 and 3 had a novel deletion (c.1140del86) inherited from their unaffected mother. MECP2 gene mutations may be considered a rare cause of MR in males although great phenotypic variation hinders genotype-phenotype correlation.

A novel p.Arg970X mutation in the last exon of the CDKL5 gene resulting in late-onset seizure disorder

Classic Rett Syndrome (RS) is a neurodevelopmental disorder due to mutations in the MECP2 gene in Xq28. Atypical RS with severe early-onset encephalopathy and therapy-resistant epilepsy can be due to mutations in the CDKL5 (Cyclin-Dependent Kinase-like 5) gene in Xp22. We here report a 14-year-old female with a RS-like clinical picture, and well-controlled seizures. MECP2 gene testing was negative, but subsequent sequencing of the CDKL5 gene revealed the c. 2908 C>T nonsense mutation (p.Arg970X) in the last exon, not previously described in other patients or controls. The less severe phenotype might be due to the position of the mutation in the last exon of the CDKL5 gene.

A substitution involving the NLGN4 gene associated with autistic behavior in the Greek population

Autism is a neurodevelopmental disorder characterized by clinical, etiologic, and genetic heterogeneity. During the last decade, predisposing genes and genetic loci were under investigation. Recently, mutations in two X-linked neuroligin genes, neuroligin 3 (NLGN3) and neuroligin 4 (NLGN4), have been implicated in the pathogenesis of autism. In our ongoing survey, we screened 169 patients with autism for mutations linked with autism. In the preliminary study of specific exons of NLGN3 and NLGN4 genes, we identified the p.K378R substitution (c.1597 A > G) in exon 5 of the NLGN4 gene in a patient who was found to have mild autism and normal IQ at 3 years of age. The same mutation has previously been found in a patient with autism. It is important that, for the first time, a specific mutation in neuroligins is confirmed in a molecular screen in another homogeneous ethnic population. This finding further contributes to consideration of neuroligins as probable candidate genes for future molecular genetic studies, suggesting that a defect of synaptogenesis may predispose to autism.

Long term follow up of a woman with classic form of Ehlers-Danlos syndrome associated with rare manifestations and review of the literature

We present the case of a 46 year-old woman with the classic type of Ehlers-Danlos syndrome who developed the rare manifestations of colon diverticula and mitral valve prolapse. We emphasize on clinical features and complications associated to this type of the syndrome, which gradually developed in our patient. A review of the literature referring to the epidemiology, molecular basis and manifestations of the classic type Ehlers-Danlos syndrome is also discussed.

Cell-free DNA levels in acute myocardial infarction patients during hospitalization

OBJECTIVES

The objectives of this study were to investigate cell-free DNA daily concentration changes following an acute myocardial infarction (AMI) and to assess any correlations with complications during hospitalization.

METHODS AND RESULTS

Serial cell-free DNA level determinations were performed by quantitative Real-Time PCR in 47 AMI patients once daily during hospitalization (235 samples) and once in 100 healthy subjects. Cell-free DNA concentrations are significantly higher in patients throughout hospitalization compared to healthy subject levels (2.644 (SE 0.0952) vs. 1.519 (SE 0.0566), P < 0.001). The median maximum cell-free DNA concentration was 3.5-fold higher (Mann Whitney P = 0.0035) in 20/47 patients with complicated post AMI course--group I--(1719.7, range 117.32-4996212.1 GenEq/ml plasma) compared with 27/47 patients without complications--group II--(492.9, range 56.43-4715.15 GenEq/ml plasma). Substantial differences exist between cell-free DNA concentrations measured on t(pre) (the day before the complication) and t(c) (the day the complication occurred) as well as t(post) (the day after the complication) in group I whereby cell-free DNA rises significantly in t(c) and remains elevated in t(post) (t(pre) vs. t(c), 2.445 vs. 2.965, P = 0.0171 and t(pre) vs. t(post) 2.445 vs. 2.913, P = 0.023).

CONCLUSIONS

Cell-free DNA concentrations were elevated in AMI patients compared to healthy control subjects, rise significantly when complications occur and have a potential clinical value in monitoring patient progress during hospitalization.

Unilateral microtia in an infant with trisomy 18 mosaicism

Trisomy 18 is the second most frequent autosomal aneuploidy, after Down's syndrome, in humans. It causes severe congenital abnormalities and mental retardation although phenotypic features, clinical manifestations and prognosis vary occasionally. In cases oftrisomy 18 mosaicism, as in every chromosomal mosaicism, the spectrum of clinical characteristics extends from pathological to almost normal. We report a 9 months old female infant who has been referred to the Genetics Department for evaluation because of unilateral severe microtia, aplasia of mastoid abscess and hemifacial palsy and inlet type intraventricular defect with pulmonary hypertension. Chromosomal investigation revealed a mosaic trisomy 18 [46,XX/47,XX+18] in proportion of 52% and 48% respectively. Microtia/anotia is present in 1.46-4.36/10,000 live births in the general population while the combination of microtia/anotia with trisomy 18 has been reported in very few cases in the relevant bibliography.

Okamoto syndrome in a girl of Caucasian origin

We report the clinical and genetic evaluation of a 2-year-old Greek female with striking phenotypic similarities to the three previously published cases of Okamoto syndrome. The main features were characteristic facies, cleft palate, generalized hypotonia, severe developmental delay, congenital hydronephrosis, and congenital heart defects. Routine chromosome testing and whole-genome high-resolution comparative genetic hybridization analysis were negative for any gross numerical or structural chromosome aberrations and for microdeletions/duplications of more than 3 million base pairs respectively. Fluorescence in situ hybridization analysis for 22q11.2 deletion and DNA analysis of the protein tyrosine phosphatase, non-receptor type II gene were normal, thus excluding DiGeorge and Noonan syndromes. Our patient did not show most of the cardinal features of Schinzel-Giedion, otopalatodigital, and C-trigonocephaly syndromes. Moreover, in our patient some new malformations were identified: unilateral kidney hypoplasia and severe anal stenosis. The latter was considered as pertinent and is described here to establish a wider clinical spectrum of Okamoto syndrome. At the age of 3 years 6 months the child continues to show severe growth failure and significant global developmental delay. For the practising paediatrician it is prudent to bear Okamoto syndrome in mind, especially in children with learning disability and a pattern of dysmorphic features.

Androgen insensitivity syndrome: clinical features and molecular defects

The end-organ resistance to androgens has been designated as androgen insensitivity syndrome (AIS), an X-linked disorder caused by mutations in the androgen receptor (AR) gene. It is generally accepted that defects in the AR gene prevent the normal development of both internal and external genital structures in 46,XY individuals, causing a variety of phenotypes ranging from male infertility to completely normal female external genitalia. Precise diagnosis requires clinical, hormonal and molecular investigation and is of great importance for appropriate gender assignment and management in general. The complexity of phenotypic presentation of AIS with genotype-phenotype variability of identical mutations complicates both the diagnostic procedure and genetic counseling of the affected families. More than 400 different AR gene mutations have thus far been reported but the receptor structure-function relationship and its phenotypic outcome is not yet fully understood. This review focuses on the clinical features and molecular pathophysiology of AIS and explores the relationship of the molecular defects in the AR gene to their clinical expression.

Rhabdomyosarcoma in a patient with Noonan syndrome phenotype and review of the literature

An increased risk of different types of malignancy has been reported in patients with Noonan syndrome (NS). We describe a patient with short stature, dysmorphic features, developmental delay, and congenital cardiomyopathy. At 5 years old, he presented with abdominal pain, constipation, and evaluation with ultrasound and computed tomography scan demonstrated the presence of an abdominal mass. Total resection of the mass and consequent histology revealed an embryonal rhabdomyosarcoma. Rhabdomyosarcoma is a rare tumor in NS patients and to the best of our knowledge only 2 cases have been reported so far. The presentation underlines the importance of frequent follow-up of patients with NS, since the incidence of malignancy is low but existing.

Spontaneous ovulation in a true hermaphrodite with normal male phenotype and a rare 46,XX/47,XXY Klinefelter's mosaic karyotype

BACKGROUND

Most true hermaphrodite patients--characterized by the presence of both ovarian and testicular tissue--demonstrate ambiguous genitalia and are diagnosed at birth, most commonly bearing a 46,XX karyotype.

PATIENT AND METHODS

We report on a 13-year-old boy presenting with left scrotal hemorrhage. He had a left inguinal hernia, a palpable testis in the right, normal male external genitalia and significant gynecomastia. During operation, the left gonad and adjacent tissue were removed for histological examination, which revealed the presence of a normal ovary, rich in follicles and a ruptured corpus luteum, suggestive of spontaneous ovulation, with a normal ipsilateral adnexa and semi-uterus. Biopsy of the right gonad revealed a dysgenetic testicle. Endocrinological assessment postoperatively depicted high FSH, pubertal testosterone and low estradiol levels. Cytogenetic analysis in peripheral blood lymphocytes and FISH of the right gonad revealed a 46,XX (70-60%)/47,XXY (30-40%) karyotype, respectively, while molecular analysis verified the presence of SRY and azoospermia factor genes.

CONCLUSION

The importance of full histological, cytogenetic and molecular investigation and of interdisciplinary approach in every single patient with sex differentiation disorders is highlighted by this rare case of spontaneous ovulation in a true hermaphrodite with normal male external genitalia and Klinefelter mosaicism.

Steroid hormones polymorphisms and cholelithiasis in Greek population

BACKGROUND

Genetic variation in genes involved in steroid biosynthesis, metabolism and signal transduction have been suggested to play a role in gallstone disease.

METHODS

To elucidate the possible role of genetic variation in the estrogen receptors alpha and beta (ER-alpha, ER-beta) and androgen receptor (AR) genes in breast cancer risk, the -1174(TA)n, c.1092+3607(CA)(n) and c.172(CAG)n repeat polymorphisms of the three genes were studied. A case-control cohort of 99 patients with cholelithiasis and 179 controls were used.

RESULTS

No significant difference was observed in the frequency distribution of -1174(TA)(0-26) in the ER-alpha gene between patients and controls, while a significant difference was observed in the frequency distribution of repeat polymorphism c.1092+3607(CA)5-27 and c.172(CAG)5-32 in the ER-beta gene and AR gene, respectively (P< or =0.001 and P=0.05, respectively). A significant difference was observed in the repeat genotype distribution (SS, SL, LL) in the (CA)n of the ER-beta gene (P<0.0001) and in the (CAG)n of the AR gene (P< or =0.0001). A significantly decreased odds ratio for cholelithiasis risk was observed in individuals having the SL and LL genotype for ER-beta gene compared with SS genotype (OR=0.212; 95% CI 0.105-0.426; P<0.0001 and OR=0.042; 95% CI 0.018-0.097, respectively) and LL genotype for AR gene (OR=0.622; 95% CI 0.345-1.121; P=0.114 and OR=0.287; 95% CI 0.151-0.543, P<0.0001, respectively). This protective effect of SL and LL genotypes for ER-beta and LL for AR gene remained evident (P<0.0001 for all of them) even after adjustment for various risk factors.

CONCLUSIONS

In conclusion an association for cholelithiasis risk between short alleles for both c.1092+3607(CA)5-27 and c.172(CAG)5-32 repeat polymorphisms of the ER-beta and AR was found in individuals of Greek descent.

Saethre-Chotzen syndrome with severe developmental delay associated with deletion of chromosomic region 7p15 --> pter

Saethre-Chotzen syndrome represents one of the most common types of craniosynostosis inherited as an autosomal dominant disorder while sporadic cases have also been reported. It is characterized by high penetrance and variable expressivity, leading to difficulties in clinical diagnosis. Some patients, who exhibit most of the diagnostic criteria of Saethre-Chotzen syndrome, have structural abnormalities of chromosome 7. The case of a 4 year old boy with notable dysmorphic features compatible with Saethre-Chotzen syndrome and severe developmental delay is described. Conventional and molecular cytogenetic analysis of peripheral blood samples from the patient and his parents revealed partial monosomy of chromosomal region 7p15 --> pter de novo. The TWIST gene, located on chromosome 7p21.1, is thought to be a negative transcriptional regulator involved in osteoblast differentiation and maturation and it is thought that haploinsufficiency of the gene can cause the disorder. The diagnosis of Saethre-Chotzen syndrome and the identification of the chromosomal abnormality in the patient facilitated genetic counseling of the family.

Does the rare A172G mutation of PTPN11 gene convey a mild Noonan syndrome phenotype?

BACKGROUND

Noonan syndrome NS (OMIM 163950) is an autosomal dominant developmental disorder characterized mainly by typical facial dysmorphism, growth retardation and variable congenital heart defects. In unrelated individuals with sporadic or familial NS, heterozygous missense point mutations in the gene PTPN11 (OMIM 176876) have been confirmed, with a clustering of mutations in exons 3 and 8, the mutation A922G Asn308Asp accounting for nearly 25% of cases.

PATIENT AND METHODS

We report a 7-year-old boy with short stature and some other clinical features of NS, who has been investigated by molecular analysis for the presence of mutations in the PTPN11 gene.

RESULT

The de novo mutation A172G in the exon 3 of the PTPN11 gene, predicting an Asn58Asp substitution, has been found. To the best of our knowledge, this specific mutation has only been described once before, but this is the first report of detailed clinical data suggesting a mild phenotype.

CONCLUSION

Detailed clinical phenotype in every patient with major or minor features of NS and molecular identification of PTPN11 gene mutation may contribute to a better phenotype-genotype correlation.

Clinical manifestations in 17 Greek patients with Goldenhar syndrome

Goldenhar (GS) syndrome is a well-recognised developmental disorder involving first and second branchial arches and characterized by considerable phenotypic variability. The present study presents clinical data on the morphologic features, hearing, ophthalmologic, orthopaedic, neurological, cardiovascular, genitourinary and gastrointestinal evaluation of 17 Greek patients (one pair of monozygotic twins) aged 20 days to 23 years with the clinical diagnosis of GS and with a normal karyotype. The most consistent findings were auricular defects (94%), followed by facial (76%) and ocular anomalies (65%), 70% unilateral, mainly right-sided. In the majority of our patients (90%) mandibular hypoplasia was ipsilateral to the dysplastic ear or the most severely affected ear in bilateral cases. Hearing loss, mainly conductive, was noted in 76% of our patients. Skeletal defects were evident in 23%, while cardiovascular, genitourinary and gastrointestinal in 18%, 23% and 12% respectively. The most frequent neurological manifestation was facial nerve paralysis (12%), while the incidence of mental retardation was higher (23%) than reported in the literature, presumably attributed to the severe hearing and vision loss. In a pair of monozygotic twins of our study discordance of clinical findings was noted. Precise evaluation of GS patients and multidisciplinary care management is necessary to avoid possible complications of many systems and to offer appropriate genetic counselling to the family.

Identification of high frequency of Y chromosome deletions in patients with sex chromosome mosaicism and correlation with the clinical phenotype and Y-chromosome instability

A mosaic karyotype consisting of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome is relatively common and is associated with a wide spectrum of clinical phenotypes. The aim of this study was to investigate patients with such a mosaic karyotype for Y chromosome material loss and then study the possible association of the absence of these regions with the phenotype, diagnosis, and Y-chromosome instability. We studied 17 clinically well-characterized mosaic patients whose karyotype consisted of a 45,X cell line and a second cell line containing a normal or an abnormal Y chromosome. The presence of the Y chromosome centromere was verified by fluorescence in situ hybridization (FISH) and was then characterized by 44 Y-chromosome specific-sequence tagged site (STS) markers. This study identifies a high frequency of Yq chromosome deletions (47%). The deletions extend from interval 5 to 7 sharing a common deleted interval (6F), which overlaps with the azoospermia factor region (AZF) region. This study finds no association between Y-chromosome loci hosting genes other than SRY, and the phenotypic sex, the diagnosis, and the phenotype of the patients. Furthermore, this study shows a possible association of these deletions with Y-chromosome instability.

Detection of 22q11.2 deletion among 139 patients with Di George/Velocardiofacial syndrome features

Cytogenetic and FISH analysis was performed in 139 patients to detect the pathognomonic of Di George/ Velocardiofacial syndrome (DGS/VFCS) deletion 22q11.2. An abnormal karyotype was revealed in 2/139 cases (47, XXY and 46, XX, 2p+). A deletion was found in 17/139 (12.2%) patients (14 males/ 3 females), inherited in 3 (2 maternal and 1 paternal). Patients with 22q11.2 deletion exhibited facial dysmorphic features (82%), congenital heart defects (70%), immunological problems (47%), multiple congenital anomalies (64%), hypocalcemia (47%), mental retardation/learning difficulties (35%), cleft palate/velopharyngeal insufficiency (23.5%), seizures/hypotonia (23%) and growth retardation (12%). Among 56/139 patients with detailed available clinical data, the 22q11.2 deletion was confirmed in all cases with hypocalcemia and in over half of the cases with multiple congenital anomalies, immunological problems and hypotonia/seizures (70%, 60% and 57%, respectively). Genetic reevaluation of 39 patients without the 22q11.2 deletion contributed to the classification of 14 (37%) under different syndromes, emphasizing the need for stricter referral criteria.

Gilbert syndrome associated with beta-thalassemia

The authors investigated whether the considerable variability in serum bilirubin levels (STB) found in transfusion-dependent beta-thalassemia, beta-thal intermedia, and heterozygous beta-thalassemia individuals could be related to the coexistence of Gilbert syndrome (GS). The promoter region [A(TA)nTAA] of the bilirubin UDP-glucuronosyltransferase gene (UGT1A1) was analyzed in a total of 128 beta-thalassemia individuals (108 transfusion-dependent beta-thal patients, 20 very mild beta-thal intermedia) and in 33 beta-thal heterozygotes. The control group consisted of 70 healthy children with no history of anemia. The frequency of GS genotype (TA)7/(TA)7 did not differ significantly between the groups studied. A significant difference was observed between serum bilirubin levels (STB) and GS genotypes (TA)7/(TA)7 and (TA)6/(TA)7 and also between (TA)7/(TA)7 and (TA)6/(TA)6 for all groups examined. These results confirm that the (TA)7/(TA)7 GS genotype is one of the factors accounting for the hyperbilirubinemia observed in beta-thalassemia major, intermedia, and heterozygous individuals.

Origin of nondisjunction in trisomy 8 and trisomy 8 mosaicism

Causes of chromosomal nondisjunction is one of the remaining unanswered questions in human genetics. In order to increase our understanding of the mechanisms underlying nondisjunction we have performed a molecular study on trisomy 8 and trisomy 8 mosaicism. We report the results on analyses of 26 probands (and parents) using 19 microsatellite DNA markers mapping along the length of chromosome 8. The 26 cases represented 20 live births, four spontaneous abortions, and two prenatal diagnoses (CVS). The results of the nondisjunction studies show that 20 cases (13 maternal, 7 paternal) were probably due to mitotic (postzygotic) duplication as reduction to homozygosity of all informative markers was observed and as no third allele was ever detected. Only two cases from spontaneous abortions were due to maternal meiotic nondisjunction. In four cases we were not able to detect the extra chromosome due to a low level of mosaicism. These results are in contrast to the common autosomal trisomies (including mosaics), where the majority of cases are due to errors in maternal meiosis.

A case of non-Fanconi anemia bone marrow dysfunction with familial involvement

We report on a Greek girl with pancytopenia, short stature, clinodactyly, cleft palate, exopthalmus, strabismus, café-au-lait spots, and mild mental retardation in whom chromosomal analysis excluded Fanconi anemia. The occurrence of erythroleukemia in the family and the presence of macrocytosis in her father and low blood counts in her sister favor the diagnosis of an inherited syndrome of familial marrow dysfunction rather than that of a sporadic case.

Detection and incidence of cryptic Y chromosome sequences in Turner syndrome patients

The presence of Y chromosome sequences in Turner syndrome (TS) patients may predispose them to gonadoblastoma formation with an estimated risk of 15-25%. The aim of this study was to determine the presence and the incidence of cryptic Y chromosome material in the genome of TS patients. The methodology involved a combination of polymerase chain reaction (PCR) and nested PCR followed by Southern blot analysis of three genes the sex determining region Y (SRY), testis specific protein Y encoded (TSPY) and RNA binding motif protein (RBM) (previously designated as YRRM) and nine additional STSs spanning all seven intervals of the Y chromosome. The methodology has a high sensitivity as it detects one 46,XY cell among 10(5) 46,XX cells. Reliability was ensured by taking several precautions to avoid false positive results. We report the results of screening 50 TS patients and the identification of cryptic Y chromosome material in 12 (24%) of them. Karyotypes were divided in four groups: 5 (23.8%) patients out of the 21 TS patients which have the 45,X karyotype (group A) also have cryptic Y sequences; none (0%) of the 7 patients who have karyotypes with anomalies on one of the X chromosomes have Y mosaicism (group B); 1 (6.3%) of the 16 patients with a mosaic karyotype have Y material (group C); and 6 (100%) out of 6 patients with a supernumerary marker chromosome (SMC) have Y chromosome sequences (group D). Nine of the 12 patients positive for cryptic Y material were recalled for a repeat study. Following new DNA extraction, molecular analysis was repeated and, in conjunction with fluorescent in situ hybridization (FISH) analysis using the Y centromeric specific probe Yc-2, confirmed the initial positive DNA findings. This study used a reliable and sensitive methodology to identify the presence of Y chromosome material in TS patients thus providing not only a better estimate of a patient's risk in developing either gonadoblastoma or another form of gonadal tumor but also the overall incidence of cryptic Y mosaicism.

Supernumerary marker chromosomes (SMCs) in Turner syndrome are mostly derived from the Y chromosome

DNA and FISH (fluorescence in situ hybridization) analysis were carried out in 12 patients with stigmata of Turner syndrome to determine whether the Supernumerary Marker Chromosome (SMC) found cytogenetically in each of these patients was derived from the Y chromosome. The presence of a Y chromosome in these patients may predispose them to develop gonadoblastoma. PCR-Southern blot analysis, followed by FISH, was used to detect the presence of Y chromosome material. The Sex determining Region Y (SRY), Testis Specific Protein Y-encoded (TSPY) and Y-chromosome RNA Recognition Motif (YRRM) genes, which map at Yp11.31, Yp11.1-11.2 and Yp11.2/Yq11.21-11.23, respectively, were selected as markers, because they span the whole Y chromosome, and more importantly, they are considered to be involved in the development of gonadoblastoma. It was shown that in 12 patients, all of whom had an SMC, the SMC of 11 was derived from the Y chromosome. Furthermore, the presence of the SRY, TSPY and YRRM gene sequences was determined and FISH analysis confirmed the Y origin of the SMCs. The methodology described in this report is a rapid, reliable and sensitive approach which may be easily applied to determine the Y origin of an SMC carried in Turner syndrome. The identification of an SMC is important for the clinical management and prognostic counseling of these patients with Turner syndrome.

High nitrate content in drinking water: cytogenetic effects in exposed children

The potential genotoxicity of nitrates and nitrites-contaminants of drinking water that have been implicated in carcinogenesis-was investigated in this study. Sister chromatid exchanges and frequency of chromatid/chromosome aberrations were studied in peripheral blood lymphocytes of 70 children who were 12-15 y of age. These children were permanent residents in geographical areas of Greece, where elevated concentrations of nitrates (i.e., 55.70-87.98 mg/l) existed in drinking water. The control group comprised 20 healthy children who resided in areas with very low nitrate concentrations (i.e., 0.7 mg/l). A significant increase in the mean number of chromatid/chromosome breaks was observed in children exposed to nitrate concentrations that exceeded 70.5 mg/l (p < .01), but there was no significant increase in the mean number of sister chromatid exchanges per cell. The results indicate that chronic administration of elevated concentrations of nitrate in drinking water has the capability of inducing cytogenetic effects.

Partial disomy of Xp and the presence of SRY in a phenotypic female

We present a study of a mentally retarded and mildly dysmorphic female in whom initial cytogenetic studies identified the karyotype 46,X, + mar. Further characterisation of the structurally abnormal chromosome by fluorescence in situ hybridisation (FISH) showed that it is composed of both X and Y chromosome material with a centromere originating from the Y chromosome. The presence of the DMD gene and the absence of the XIST gene was shown by FISH using locus specific probes. The Y segment included the SRY and ZFY genes. Based on these findings, the karyotype was defined as 46, X,der(Y)t(X;Y) (p21.1;q11). This case illustrates male to female sex reversal owing to a partial duplication of the short arm of the X chromosome in the presence of SRY.