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PurposeTo describe our experience of offering simultaneous genetic carrier screening for cystic fibrosis (CF), fragile X syndrome (FXS), and spinal muscular atrophy (SMA).MethodsCarrier screening is offered through general practice, obstetrics, fertility, and genetics settings before or in early pregnancy. Carriers are offered genetic counseling with prenatal/preimplantation genetic diagnosis available to those at increased risk.ResultsScreening of 12,000 individuals revealed 610 carriers (5.08%; 1 in 20): 342 CF, 35 FXS, 241 SMA (8 carriers of 2 conditions), approximately 88% of whom had no family history. At least 94% of CF and SMA carriers' partners were tested. Fifty couples (0.42%; 1 in 240) were at increased risk of having a child with one of the conditions (14 CF, 35 FXS, and 1 SMA) with 32 pregnant at the time of testing. Of these, 26 opted for prenatal diagnosis revealing 7 pregnancies affected (4 CF, 2 FXS, 1 SMA).ConclusionThe combined affected pregnancy rate is comparable to the population risk for Down syndrome, emphasizing the need to routinely offer carrier screening. The availability of appropriate genetic counseling support and a collaborative approach between laboratory teams, genetics services, health professionals offering screening, and support organizations is essential.

Aim Despite advances in medical investigation, many children with neurological conditions remain without a diagnosis, although a genetic aetiology is often suspected. Chromosomal microarray (CMA) screens for copy number variants (CNVs) and long continuous stretches of homozygosity (LCSH) and may further enhance diagnostic yield. Although recent studies have identified pathogenic CNVs in intellectual disability, autism and epilepsy, the utility of CMA testing in a broader cohort of children with neurologic disorders has not been reported. Methods Two hundred fifteen patients with neurological conditions of unknown aetiology were seen over a 6-month period and were prospectively tested by CMA using high-resolution single nucleotide polymorphism (SNP) microarrays (Illumina HumanCytoSNP-12 v2.1 or Affymetrix 2.7M). Results Thirty of 215 (14%) patients tested had an abnormal CMA. Twenty-nine had CNVs (13%) and one (0.5%) a clinically significant stretch of homozygosity. Twenty (9.3%) had a CMA finding considered to be pathogenic or involved in susceptibility to the condition of interest, and 10 (4.7%) had findings of unknown significance. Their phenotypes included infantile spasms and other epilepsies, neuromuscular conditions, ataxia, movement disorders, microcephaly and malformations of cortical development. At least one third of patients did not meet national funding criteria for CMA at the time of presentation. Conclusions CMA detected clinically significant abnormalities in a broad range of neurologic phenotypes of unknown aetiology. This test should be considered a first-tier investigation of children with neurologic disorders in whom the initial clinical assessment does not indicate a likely aetiology, especially those with severe epilepsies and neurologically abnormal neonates.

Contains fulltext : 89801.pdf (Publisher’s version ) (Closed access) Periventricular heterotopia (PH) is a brain malformation characterised by heterotopic nodules of neurons lining the walls of the cerebral ventricles. Mutations in FLNA account for 20-24% of instances but a majority have no identifiable genetic aetiology. Often the co-occurrence of PH with a chromosomal anomaly is used to infer a new locus for a Mendelian form of PH. This study reports four PH patients with three different microdeletion syndromes, each characterised by high-resolution genomic microarray. In three patients the deletions at 1p36 and 22q11 are conventional in size, whilst a fourth child had a deletion at 7q11.23 that was larger in extent than is typically seen in Williams syndrome. Although some instances of PH associated with chromosomal deletions could be attributed to the unmasking of a recessive allele or be indicative of more prevalent subclinical migrational anomalies, the rarity of PH in these three microdeletion syndromes and the description of other non-recurrent chromosomal defects do suggest that PH may be a manifestation of multiple different forms of chromosomal imbalance. In many, but possibly not all, instances the co-occurrence of PH with a chromosomal deletion is not necessarily indicative of uncharacterised underlying monogenic loci for this particular neuronal migrational anomaly. 01 februari 2010

We provide the first description of a patient with a heterozygous deletion of the Attractin-like (ATRNL1) gene. The patient presented with a novel and distinctive phenotype comprising dysmorphic facial appearance, ventricular septal defect, toe syndactyly, radioulnar synostosis, postnatal growth retardation, cognitive impairment with autistic features, and ataxia. A 325 kb de novo deletion in ATRNL1 was demonstrated using SNP microarray and confirmed by FISH analysis using BAC probes. Sequence analysis of the undeleted allele did not identify any alterations, suggesting that the phenotype was the result of haploinusfficiency. ATRNL1 and its paralog ATRN are highly conserved transmembrane proteins thought to be involved in cell adhesion and signalling events. The phenotype of mice with homozygous Atrn mutations overlaps considerably with the features observed in our patient. We therefore postulate that our patient’s phenotype is caused by the deletion of ATRNL1, and provide further insight into the role of ATRNL1 in human development.

Background Several recent studies have demonstrated the use of single nucleotide polymorphism (SNP) arrays for the investigation of intellectual disability, developmental delay, autism or congenital abnormalities. In addition to LogR ‘copy number’ data, these arrays provide SNP genotyping data for gene level autozygosity mapping, estimating low levels of mosaicism, assessing long continuous stretches of homozygosity (LCSH), detection of uniparental disomy, and ‘autozygous’ regions. However, there remains little specific information on the clinical utility of this genotyping data. Methods Molecular karyotyping, using SNP array, was performed on 5000 clinical samples. Results Clinically significant ‘LogR neutral’ genotyping abnormalities were detected in 0.5% of cases. Among these were a single case of chimerism, 12 cases with low level chromosome mosaicism, and 11 cases with an LCSH associated with uniparental disomy. In addition, the genotyping data revealed several LCSH associated with clinically relevant ‘recessive type’ genetic defects. Conclusions These results demonstrate the utility of SNP genotyping data for detection of clinically significant abnormalities, including chimerism/mosaicism and recessive Mendelian disorders associated with autozygosity. The incidence of clinically significant low level mosaicism inferred from these cases suggests that this has hitherto been underestimated and chromosome mosaicism frequently occurs in the absence of indicative clinical features. The growing appreciation among clinicians and demand for SNP genotyping data poses significant challenges for the interpretation of LCSH, especially where there is no detailed phenotypic description to direct laboratory analysis. Finally, reporting of unexpected or hidden consanguinity revealed by SNP array analysis raises potential ethical and legal issues.

Contains fulltext : 88561.pdf (Publisher’s version ) (Closed access) BACKGROUND: Chromosome 17p13.3 contains extensive repetitive sequences and is a recognised region of genomic instability. Haploinsufficiency of PAFAH1B1 (encoding LIS1) causes either isolated lissencephaly sequence or Miller-Dieker syndrome, depending on the size of the deletion. More recently, both microdeletions and microduplications mapping to the Miller-Dieker syndrome telomeric critical region have been identified and associated with distinct but overlapping phenotypes. METHODS: Genome-wide microarray screening was performed on 7678 patients referred with unexplained learning difficulties and/or autism, with or without other congenital abnormalities. Eight and five unrelated individuals, respectively, were identified with microdeletions and microduplications in 17p13.3. RESULTS: Comparisons with six previously reported microdeletion cases identified a 258 kb critical region, encompassing six genes including CRK (encoding Crk) and YWHAE (encoding 14-3-3epsilon). Clinical features included growth retardation, facial dysmorphism and developmental delay. Notably, one individual with only subtle facial features and an interstitial deletion involving CRK but not YWHAE suggested that a genomic region spanning 109 kb, encompassing two genes (TUSC5 and YWHAE), is responsible for the main facial dysmorphism phenotype. Only the microduplication phenotype included autism. The microduplication minimal region of overlap for the new and previously reported cases spans 72 kb encompassing a single gene, YWHAE. These genomic rearrangements were not associated with low-copy repeats and are probably due to diverse molecular mechanisms. CONCLUSIONS: The authors further characterise the 17p13.3 microdeletion and microduplication phenotypic spectrum and describe a smaller critical genomic region allowing identification of candidate genes for the distinctive facial dysmorphism (microdeletions) and autism (microduplications) manifestations. 01 mei 2010

Microdeletions at 14q12 that include FOXG1, or loss of function mutations in FOXG1, are associated with the congenital variant of Rett syndrome. By SNP microarray analysis we identified a corresponding microduplication at 14q12 in a nine year old girl with symptomatic generalised epilepsy, severe intellectual impairment, and minor dysmorphisms, but without microcephaly. The 14q12 microduplication comprised 4.45 Mb of DNA and included FOXG1. This is the first report of duplication involving FOXG1 and suggests a dosage sensitive role for FOXG1 in brain development.

Prenatal diagnosis of syndromes caused by chromosomal abnormality is a long established part of obstetric care in developed countries. In this area, there have been recent significant advances in the identification of high risk pregnancies using sophisticated serum analyte and ultrasound screening methods.1,2 For follow up diagnostic testing, karyotyping has provided the gold standard. This technology has remained essentially unchanged over 30 years, as no new technology has yet proven superior in terms of being able to detect such a wide range of abnormalities with the necessary precision. Nevertheless, molecular tests, such as fluorescent in situ hybridisation (FISH) 3 and short tandem repeat analysis,4 are now in common practice for the diagnosis of specific abnormalities. These adjunctive tests importantly decrease turnaround times from 1–2 weeks to 1–2 days. We assessed the performance of multiplex ligation dependent probe amplification (MLPA) as an alternative method for the detection of aneuploidy, which is by far the most common prenatal chromosome abnormality. This novel technique5 detects sequence dosage differences in a semi-quantitative manner and has many potential applications in diagnostic molecular genetics and cytogenetics. For example, a recent report describes its use for detection of large genomic deletions and duplications in the BRCA1 gene.6 This technology appears to have significant advantages in that it is extremely versatile in its applications, flexible in its target loci, highly automated, suitable for high throughput testing, efficient, and cost effective. Its application for aneuploidy detection has not been reported in a clinical setting. In order to assess the precision and robustness of the test, we conducted a prospective blind trial on 492 consecutive amniocentesis samples referred to our cytogenetics laboratory. ### Study design This study was designed to blind test amniocentesis samples prospectively. The samples were collected over a 4 month period as they were referred …