Beta-thalassemia is the most common hereditary disease in Iran. More than two million carriers of beta-thalassemia live in Iran. Since the Iranian population is a mixture of different ethnic groups, it is necessary to determine the frequency and distribution of mutations in the different parts of the country. For this purpose, we divided Iran in to eight different regions according to the geographic and ethnic distribution of the population. Over a 10-year period 1,217 beta-thalassemia chromosomes of 164 affected patients and 889 unrelated carriers were studied using the amplification refractory mutation system-polymerase chain reaction technique. We detected 81% beta-thalassemia mutations in the studied chromosomes. IVS-II-I (G --> A) was the predominant mutation found in our study (34%). Its relative frequency in the north was much higher than other regions, and it lessened toward the south, where the IVS-I-5 (G --> C) mutation was more common. IVS-I-5 (G --> C) (7.55%), codons 8/9 (+ G) (4.76%), and IVS-I-110 (G --> A) (4.76%) were the other most common mutations. The results presented here can be used as a basis of prenatal diagnosis of beta-thalassemia in different regions of Iran.

Mucopolysaccharidosis III D (Sanfilippo disease type D, MPS IIID) is a rare autosomal recessive lysosomal storage disorder previously described in only 20 patients. MPS IIID is caused by a deficiency of N-acetylglucosamine-6-sulphate sulphatase (GNS), one of the enzymes required for the degradation of heparan sulphate. So far only seven mutations in the GNS gene have been reported. The clinical phenotype of 12 new MPS IIID patients from 10 families was studied. Mutation analysis of GNS was performed in 16 patients (14 index cases). Clinical signs and symptoms of the MPS IIID patients appeared to be similar to previously described patients with MPS III. Early development was normal with onset of behavioral problems around the age of 4 years, followed by developmental stagnation, deterioration of verbal communication and subsequent deterioration of motor functions. Sequence analysis of the coding regions of the gene encoding GNS (GNS) resulted in the identification of 15 novel mutations: 3 missense mutations, 1 nonsense mutation, 4 splice site mutations, 3 frame shift mutations, 3 large deletions and 1 inframe small deletion. They include the first missense mutations and a relatively high proportion of large rearrangements, which warrants the inclusion of quantitative techniques in routine mutation screening of the GNS gene.

We report on a 1-year-old boy with craniosynostosis, microcephaly, developmental delay and dysmorphic features. Chromosomal studies of the proband showed 46,XY,add(2)(q37)dn and those of the parents were normal. The rearranged material in the patient was further defined using array comparative genomic hybridization (array CGH), which revealed loss of 2Mb distal to 2q37.3 and duplication of 15Mb from 5q34 --> qter. Fluorescence in situ hybridization (FISH) studies using subtelomeric 2q and 5q probes showed the 2q deletion and 5q duplication resulting from a rearrangement of the segment from 5q onto the long arm of chromosome 2. FISH studies of the parents did not show any rearrangement. Recently it has been proposed that an extra copy of MSX2 that maps to 5q35.2 causes premature synostosis of the sutures via the MSX2-mediated pathway of calvarial osteogenic differentiation. Our case further supports the role of MSX2 duplication in the etiology of craniosynostosis.

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Williams-Beuren syndrome (WBS) is a chromosomal microdeletion syndrome with variable phenotypic features such as supravalvular aortic stenosis (SVAS), facial appearance characteristics, growth retardation, and infantile hypercalcemia. This study aimed to detect the 7q11.23 microdeletion in 10 patients with early clinical diagnosis of WBS using fluorescent in situ hybridization or array comparative genomic hybridization. As an alternative method, multiplex ligation-dependent probe amplification (MLPA) was used to confirm this microdeletion. Clinical features were also compared with detected genotypes. To reveal the parental origin of deletion, four polymorphic markers (D7S1870, D7S489, D7S613, and D7S2476) were used. The deletion had maternal origin in 80% and paternal origin in 20% of the cases. From 10 patients with early clinical diagnosis of the WBS, 3 patients presented with atypical phenotypes such as infantile hypocalcemia, normal IQ, and normal facial characterization, but the sizes of their deletions seemed to be almost similar to other cases. Regarding such observation, we suggest that the phenotypic variations of WBS are influenced not only by the deletion size and involving genes but also by the breakpoint regions and probably epigenetic effects. However, further research is required to explore the effect of such parameters on phenotypic features.

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BACKGROUND:Mental retardation (MR) has a prevalence of 1-3% and genetic causes are present in more than 50% of patients. Chromosomal abnormalities are one of the most common genetic causes of MR and are responsible for 4-28% of mental retardation. However, the smallest loss or gain of material visible by standard cytogenetic is about 4 Mb and for smaller abnormalities, molecular cytogenetic techniques such as array comparative genomic hybridization (array CGH) should be used. It has been shown that 15-25% of idiopathic MR (IMR) has submicroscopic rearrangements detectable by array CGH. In this project, the genomic abnormalities were investigated in 32 MR patients using this technique.MATERIALS AND METHODS:Patients with IMR with dysmorphism were investigated in this study. Karyotype analysis, fragile X and metabolic tests were first carried out on the patients. The copy number variation was then assessed in a total of 32 patients with normal results for the mentioned tests using whole genome oligo array CGH. Multiple ligation probe amplification was carried out as a confirmation test.RESULTS:In total, 19% of the patients showed genomic abnormalities. This is reduced to 12.5% once the two patients with abnormal karyotypes (upon re-evaluation) are removed.CONCLUSION:The array CGH technique increased the detection rate of genomic imbalances in our patients by 12.5%. It is an accurate and reliable method for the determination of genomic imbalances in patients with IMR and dysmorphism.