Syndromic mental retardation with thrombocytopenia due to 21q22.11q22.12 deletion: Report of three patients.

During the last few years, an increasing number of microdeletion/microduplication syndromes have been delineated. This rapid evolution is mainly due to the availability of microarray technology as a routine diagnostic tool. Microdeletions of the 21q22.11q22.12 region encompassing the RUNX1 gene have been reported in nine patients presenting with syndromic thrombocytopenia and mental retardation. RUNX1 gene is responsible for an autosomal dominant platelet disorder with predisposition to acute myelogenous leukemia. We report on three novel patients with an overlapping "de novo" interstitial deletion involving the band 21q22 characterized by array-CGH. All our patients presented with severe developmental delay, dysmorphic features, behavioral problems, and thrombocytopenia. Comparing the clinical features of our patients with the overlapping ones already reported two potential phenotypes related to 21q22 microdeletion including RUNX1 were highlighted: thrombocytopenia with +/- mild dysmorphic features and syndromic thrombocytopenia with growth and developmental delay.

Array comparative genomic hybridization in retinoma and retinoblastoma tissues.

In retinoblastoma, two RB1 mutations are necessary for tumor development. Recurrent genomic rearrangements may represent subsequent events required for retinoblastoma progression. Array-comparative genomic hybridization was carried out in 18 eye samples, 10 from bilateral and eight from unilateral retinoblastoma patients. Two unilateral cases also showed areas of retinoma. The most frequent imbalance in retinoblastomas was 6p gain (40%), followed by gains at 1q12-q25.3, 2p24.3-p24.2, 9q22.2, and 9q33.1 and losses at 11q24.3, 13q13.2-q22.3, and 16q12.1-q21. Bilateral cases showed a lower number of imbalances than unilateral cases (P = 0.002). Unilateral cases were divided into low-level (< or = 4) and high-level (> or = 7) chromosomal instability groups. The first group presented with younger age at diagnosis (mean 511 days) compared with the second group (mean 1606 days). In one retinoma case ophthalmoscopically diagnosed as a benign lesion no rearrangements were detected, whereas the adjacent retinoblastoma displayed seven aberrations. The other retinoma case identified by retrospective histopathological examination shared three rearrangements with the adjacent retinoblastoma. Two other gene-free rearrangements were retinoma specific. One rearrangement, dup5p, was retinoblastoma specific and included the SKP2 gene. Genomic profiling indicated that the first retinoma was a pretumoral lesion, whereas the other represents a subclone of cells bearing 'benign' rearrangements overwhelmed by another subclone presenting aberrations with higher 'oncogenic' potential. In summary, the present study shows that bilateral and unilateral retinoblastoma have different chromosomal instability that correlates with the age of tumor onset in unilateral cases. This is the first report of genomic profiling in retinoma tissue, shedding light on the different nature of lesions named 'retinoma'.

Erratum to: Clinical and molecular characterization of Italian patients affected by Cohen syndrome.

The complete affiliations of two authors appeared incorrectly. The affiliations of A. Selicorni and D. Milani should be given as.

Private inherited microdeletion/microduplications: implications in clinical practice.

The introduction of array-CGH analysis is allowing the identification of novel genomic disorders. However, this new high-resolution technique is also opening novel diagnostic challenges when inherited private CNVs of unclear clinical significance are found. Oligo array-CGH analysis of 84 patients with mild to severe mental retardation associated with multiple congenital anomalies revealed 10 private CNVs inherited from a healthy parent. Three were deletions (7q31, 14q21.1, Xq25) and seven duplications (12p11.22, 12q21.31, 13q31.1, 17q12, Xp22.31, Xq28) ranging between 0.1 and 3.8Mb. Six rearrangements were not polymorphic. Four overlapped polymorphic regions to the extent of 10-61%. In one case the size was different between the proband and the healthy relative. Three small rearrangements were gene deserts. The remaining seven had a mean gene content of five (ranging from 1 to 18). None of the rearranged genes is known to be imprinted. Three disease-genes were found in three different cases: KAL1 in dupXp22.31, STS in another dupXp22.31 and TCF2 in dup17q12. The patient carrying the last duplication presents sex reversal, Peters' anomaly and renal cysts and the duplication is located 4Mb away from the HSD17B1 gene, coding a key enzyme of testosterone biosynthesis. Considering the overlap with polymorphic regions, size-identity within the family, gene content, kind of rearrangement and size of rearrangement we suggest that at least in five cases the relationship to the phenotype has not to be excluded. We recommend to maintain caution when asserting that chromosomal abnormalities inherited from a healthy parent are benign. A more complex mechanism may in fact be involved, such as a concurrent variation in the other allele or in another chromosome that influences the phenotype.

A 3 Mb deletion in 14q12 causes severe mental retardation, mild facial dysmorphisms and Rett-like features.

The present report describes a 7-year-old girl with a de novo 3 Mb interstitial deletion of chromosome 14q12, identified by oligo array-CGH. The region is gene poor and contains only five genes two of them, FOXG1B and PRKD1 being deleted also in a previously reported case with a very similar phenotype. Both patients present prominent metopic suture, epicanthic folds, bulbous nasal tip, tented upper lip, everted lower lip and large ears and a clinical course like Rett syndrome, including normal perinatal period, postnatal microcephaly, seizures, and severe mental retardation. FOXG1B (forkhead box G1B) is a very intriguing candidate gene since it is known to promote neuronal progenitor proliferation and to suppress premature neurogenesis and its disruption is reported in a patient with postnatal microcephaly, corpus callosum agenesis, seizures, and severe mental retardation.

Cohen syndrome resulting from a novel large intragenic COH1 deletion segregating in an isolated Greek island population.

Cohen syndrome, caused by mutations in the COH1 gene, is an autosomal recessive disorder consisting of mental retardation, microcephaly, growth delay, severe myopia, progressive chorioretinal dystrophy, facial anomalies, slender limbs with narrow hands and feet, tapered fingers, short stature, kyphosis and/or scoliosis, pectus carinatum, joint hypermobility, pes calcaneovalgus, and, variably, truncal obesity. Here, we describe the clinical and molecular findings in 14 patients from an isolated Greek island population. The clinical phenotype was fairly homogeneous, although microcephaly was not constant, and some patients had severe visual disability. All patients were homozygous for a novel intragenic COH1 deletion spanning exon 6 to exon 16, suggesting a founder effect. The discovery of this mutation has made carrier detection and prenatal diagnosis possible in this population.

MECP2 deletions and genotype-phenotype correlation in Rett syndrome.

Rett syndrome is a neurodevelopmental disorder that represents one of the most common genetic causes of mental retardation in girls. MECP2 point mutations in exons 2-4 account for about 80% of classic Rett cases and for a lower percentage of variant patients. We investigated the genetic cause in 77 mutation-negative Rett patients (33 classic, 31 variant, and 13 Rett-like cases) by searching missed MECP2 defects. DHPLC analysis of exon 1 and MLPA analysis allowed us to identify the defect in 17 Rett patients: one exon 1 point mutation (c.47_57del) in a classic case and 16 MECP2 large deletions (15/33 classic and 1/31 variant cases). One identical intragenic MECP2 deletion, probably due to gonadal mosaicism, was found in two sisters with discordant phenotype: one classic and one "highly functioning" preserved speech variant. This result indicates that other epigenetic or genetic factors, beside MECP2, may contribute to phenotype modulation. Three out of 16 MECP2 deletions extend to the adjacent centromeric IRAK1 gene. A putative involvement of the hemizygosity of this gene in the ossification process is discussed. Finally, results reported here clearly indicate that MECP2 large deletions are a common cause of classic Rett, and MLPA analysis is mandatory in MECP2-negative patients, especially in those more severely affected (P = 0.044).

3.2 Mb microdeletion in chromosome 7 bands q22.2-q22.3 associated with overgrowth and delayed bone age.

We report a patient with mental retardation, epilepsy, overgrowth, delayed bone age, peculiar facial features, corpus callosum hypoplasia, enlarged cisterna magna and right cerebellar hypoplasia. Array-CGH analysis revealed the presence of a de novo 3.2 Mb interstitial deletion of the long arm of chromosome 7 involving bands q22.2-q22.3. The rearrangement includes 15 genes and encompasses a genomic region that represents a site of frequent loss of heterozygosity in myeloid malignancies. Four genes are implicated in the control of cell cycle: SRPK2, MLL5, RINT1 and LHFPL3. Haploinsufficiency of these genes might therefore be associated with overgrowth and could confer susceptibility to cancers or other tumours, so that attention to this possibility would be appropriate during regular medical review. In conclusion, array-CGH analysis should be performed in patients with overgrowth where the known causes have already been excluded, because some still unclassified overgrowth syndromes may be caused by subtle genomic imbalances.

High frequency of COH1 intragenic deletions and duplications detected by MLPA in patients with Cohen syndrome.

Cohen syndrome is a rare, clinically variable autosomal recessive disorder characterized by mental retardation, postnatal microcephaly, facial dysmorphisms, ocular abnormalities and intermittent neutropenia. Mutations in the COH1 gene have been found in patients from different ethnic origins. However, a high percentage of patients have only one or no mutated allele. To investigate whether COH1 copy number changes account for missed mutations, we used multiplex ligation-dependent probe amplification (MLPA) to test a group of 14 patients with Cohen syndrome. This analysis has allowed us to identify multi-exonic deletions in 11 alleles and duplications in 4 alleles. Considering our previous study, COH1 copy number variations represent 42% of total mutated alleles. To our knowledge, COH1 intragenic duplications have never been reported in Cohen syndrome. The three duplications encompassed exons 4-13, 20-30 and 57-60, respectively. Interestingly, four deletions showed the same exon coverage (exons 6-16) with respect to a deletion recently reported in a large Greek consanguineous family. Haplotype analysis suggested a possible founder effect in the Mediterranean basin. The use of MLPA was therefore crucial in identifying mutated alleles undetected by traditional techniques and in defining the extent of the deletions/duplications. Given the high percentage of identified copy number variations, we suggest that this technique could be used as the initial screening method for molecular diagnosis of Cohen syndrome.

14q12 Microdeletion syndrome and congenital variant of Rett syndrome.

Only two patients with 14q12 deletion have been reported to date. Here, we describe an additional patient with a similar deletion in order to improve the clinical delineation of this new microdeletion syndrome. The emerging phenotype is characterized by a Rett-like clinical course with an almost normal development during the first months of life followed by a period of regression. A peculiar facial phenotype is also present and it is characterized by mild dysmorphisms such as downslanting palpebral fissures, bilateral epicanthic folds, depressed nasal bridge, bulbous nasal tip, tented upper lip, everted lower lip and large ears. The relationship between this microdeletion syndrome and the congenital variant of Rett syndrome due to point mutations in one of the genes included in the deleted region, FOXG1, is discussed.

Clinical and molecular characterization of Italian patients affected by Cohen syndrome.

Cohen syndrome is an autosomal recessive disorder with variability in the clinical manifestations, characterized by developmental delay, visual disability, facial dysmorphisms and intermittent neutropenia. We described a cohort of 10 patients affected by Cohen syndrome from nine Italian families ranging from 5 to 52 years at assessment. Characteristic age related facial changes were well documented. Visual anomalies, namely retinopathy and myopia, were present in 9/10 patients (retinopathy in 9/10 and myopia in 8/10). Truncal obesity has been described in all patients older than 6 years (8/8). DNA samples from all patients were analyzed for mutations in COH1 by DHPLC. We detected 15 COH1 alterations most of them were truncating mutations, only one being a missense change. Partial gene deletions have been found in two families. Most mutations were private. Two were already reported in the literature just once. A single base deletion leading to p.T3708fs3769, never reported before, was found in three apparently unrelated families deriving from a restricted area of the Veneto's lowland, between Padova town and Tagliamento river, in heterozygous state. Given the geographical conformation of this region, which is neither geographically or culturally isolated, a recent origin of the mutation could be hypothesized.