A decade of molecular preimplantation genetic diagnosis of 350 blastomeres for beta-thalassemia combined with HLA typing, aneuploidy screening and sex selection in Iran.

BACKGROUND: Preimplantation genetic diagnosis (PGD) has been developed to detect genetic disorders before pregnancy which is usually done on blastomeres biopsied from 8-cell stage embryos obtained from in vitro fertilization method (IVF). Here we report molecular PGD results for diagnosing of beta thalassemia (beta-thal) which are usually accompanied with evaluating chromosomal aneuploidies, HLA typing and sex selection. METHODS: In this study, haplotype analysis was performed using short tandem repeats (STRs) in a multiplex nested PCR and the causative mutation was detected by Sanger sequencing. RESULTS: We have performed PGDs on 350 blastomeres from 55 carrier couples; 142 blastomeres for beta-thal only, 75 for beta-thal and HLA typing, 76 for beta-thal in combination with sex selection, and 57 for beta-thal and aneuploidy screening. 150 blastomeres were transferable, 15 pregnancies were happened, and 11 babies born. We used 6 markers for beta-thal, 36 for aneuploidy screening, 32 for sex selection, and 35 for HLA typing. To our knowledge combining all these markers together and the number of STR markers are much more than any other studies which have ever done. CONCLUSIONS: PGD is a powerful diagnostic tool for carrier couples who desire to have a healthy child and wish to avoid medical abortion.

The Spectrum of Pathogenic Variants in Iranian Families with Hemophilia A.

BACKGROUND: Hemophilia A (HA) is an X-linked recessive bleeding disorder with a high rate of genetic heterogeneity. The present study was conducted on a large cohort of Iranian HA patients and data obtained from databases. METHODS: A total of 622 Iranian HA patients from 329 unrelated families who had been referred to a medical genetics laboratory in Tehran from 2005 to 2019, were enrolled in this retrospective, observational study. Genetic screening of pathogenic variants of the F8 gene was performed using inverse shifting PCR, direct sequencing, and multiplex ligation-dependent amplification (MLPA). Point mutation frequencies in different exons were analyzed for our samples as well as 6031 HA patients whose data were recorded in a database. RESULTS: A total of 144 different pathogenic or likely pathogenic variants including 29 novel variants were identified. A strategy to decrease costs of genetic testing of HA was suggested based on this finding. CONCLUSION: This study provides comprehensive information on F8 pathogenic/likely pathogenic variants in Iranian HA patients which improves the spectrum of causative mutations and can be helpful to clinicians and medical geneticists in counseling and molecular diagnosis of HA.

Reporting a rare form of myopathy, myopathy with extrapyramidal signs, in an Iranian family using next generation sequencing: a case report.

BACKGROUND: Myopathy with extrapyramidal signs (MPXPS) is an autosomal recessive mitochondrial disorder which is caused by mutation in mitochondrial calcium uptake 1 (MICU1) gene located on chromosome 10q22.1. Next Generation Sequencing (NGS) technology is the most effective method for identification of pathogenic variants with the ability to overcome some limitations which Sanger sequencing may encountered. There are few reports on this rare disease around the world and here in this study we first revealed genetic identification of two affected individuals in an Iranian family with a novel mutation. CASE PRESENTATION: The proband was a 5-year-old girl from consanguenous parents. She was first clinically suspicious of affected with limb-girdle muscular dystrophy (LGMD). Muscle biopsy studies and autozygosity mapping, using four short tandem repeat (STR) markers linked to 6 genes of the most prevalent forms of LGMD, ruled out calpainopathy, dysferlinopathy, and sarcoglycanopathis. DNA sample of the proband was sent for NGS. Whole exome sequencing (WES) revealed a novel mutation c.1295delA in exon 13 of MICU1 gene. This homozygous deletion creates a frameshift and a premature stop codon downstream of canonical EF4 calcium binding motif of MICU1. According to the American College of Medical Genetics and Genomics (ACMG) guidline for sequence interpretation, this variant was a pathogenic one. Sanger sequencing in all family members confirmed the results of the WES. CONCLUSIONS: This study was the first report of MPXPS in Iranian population which also revealed a novel mutation in the MICU1 gene.

Development and validation of a novel panel of 16 STR markers for simultaneous diagnosis of ß-thalassemia, aneuploidy screening, maternal cell contamination detection and fetal sample authenticity in PND and PGD/PGS cases.

Prenatal diagnosis (PND) may be complicated with sample mix-up; maternal cell contamination, non-paternity and allele drop out at different stages of diagnosis. Aneuploidy screening if combined with PND for a given single gene disorder, can help to detect any common aneuploidy as well as aiding sample authenticity and other probable complications which may arise during such procedures. This study was carried out to evaluate the effectiveness of a novel panel of STR markers combined as a multiplex PCR kit (HapScreen™ kit) for the detection of ß-thalassemia, aneuploidy screening, ruling in/out maternal cell contamination (MCC), and sample authenticity. The kit uses 7 STR markers linked to ß-globin gene (HBB) as well as using 9 markers for quantitative analysis of chromosomes 21, 18, 13, X and Y. Selection of the markers was to do linkage analysis with ß-globin gene, segregation analysis and to perform a preliminary aneuploidy screening of fetal samples respectively. These markers (linked to the ß-globin gene) were tested on more than 2185 samples and showed high heterozygosity values (68.4-91.4%). From 2185 fetal cases we found 3 cases of non-paternity, 5 cases of MCC, one case of sample mix-up and one case of trisomy 21 which otherwise may have end up to misdiagnosis. This kit was also successfully used on 231 blastomeres for 29 cases of pre-implantation genetic diagnosis (PGD) and screening (PGS). The markers used for simultaneous analysis of haplotype segregation and aneuploidy screening proved to be very valuable to confirm results obtained from direct mutation detection methods (i.e. ARMS, MLPA and sequencing) and aneuploidy screening.

Impact of consanguineous marriages in GJB2-related hearing loss in the Iranian population: a report of a novel variant.

Mutations in GJB2 and GJB6 genes are the main causes of autosomal recessive nonsyndromic hearing loss (ARNSHL) in many populations. Here, we investigated GJB2 and GJB6 mutations in 114 patients from 77 affected ARNSHL families including 54 consanguineous marriages and 23 nonrelative marriages in the Iranian population. Clinical studies and genetic counseling were performed for all families. GJB2 and GJB6 genes were directly sequenced. Three known GJB6 large deletions [del(GJB6-D13S1830), del(GJB6-D13S1854), and a 920 kb deletion] were also checked by quantification of a common deleted region within the GJB6 gene. The frequency of consanguinity was 70.13% among the studied families. Biallelic GJB2 mutations were 16.67% in consanguineous marriages and 4.35% in nonrelative marriages. Mutations found were 35delG, delE120, R127H, M163V, W24X, V37I, G12D, V84A, 313-326del14, and E110K. The latter was a novel variant. Neither point mutation nor a large deletion in the GJB6 gene was found in the population. Mean frequency of GJB2 mutations was 17.92%. GJB2 mutations (and not GJB6 mutations) are the major causes of hearing loss in Iran. The role of consanguineous marriages is also highlighted in occurrence of GJB2-related hearing loss. We suggest that other genes may be involved in the population.