Biomedical subjects

Ali Hellani

Publications and source records attributed to Ali Hellani.

10 recordsLinked to original sources

PubMed2006

Y chromosome microdeletions in infertile men with idiopathic oligo- or azoospermia.

About 30-40% of male infertility is due to unknown reasons. Genetic contributions to the disruption of spermatogenesis are suggested and amongst the genetic factors studied, Y chromosome microdeletions represent the most common one. Screening for microdeletions in AZFa, b and c region of Y chromosome showed a big variation among different studies. The purpose of this study was to investigate the prevalence of such deletions in Saudi men. A total of 257 patients with idiopathic oligo- or azoospermia were screened for Y chromosome microdeletions by 19 markers in AZF region. Ten (3.9%) patients had chromosomal rearrangements, six of them showed sex chromosome abnormalities and four patients had apparently balanced autosomal rearrangements. Eight of the remaining 247 patients (3.2%) with a normal karyotype and no known causes of impaired spermatogenesis had Y chromosome microdeletions. Among these, six patients had deletions in AZFc region, one case had a deletion in AZFb and another had both AZFa and AZFc deletions.In conclusion, our study shows that Y chromosome microdeletions are low in our population. We also report for the first time a case with unique point deletions of AZFa and AZFc regions. The lower frequency of deletions in our study suggest that other genetic, epigenetic, nutritional and local factors may be responsible for idiopathic oligo- or azoospermia in the Saudi population.

Journal Article↗

PubMed2005

Y chromosome microdeletions: are they implicated in teratozoospermia?

BACKGROUND: Y chromosome microdeletions are known to impair spermatogenesis. Screenings for these microdeletions are performed mostly in patients with sperm count abnormalities. METHODS: We have screened the Y chromosome of 80 infertile patients with sperm morphological abnormalities. DNA from sperm, peripheral blood or single sperm following multiple displacement amplification (MDA) was utilized to amplify 20 specific sequence-tagged sites (STS) by PCR. RESULTS: Y chromosome microdeletions were detected in sperm DNA from four of the teratozoospermic patients; while none of the 53 men with normal sperm morphology had any deletions. Two of the four patients with deletions also provided peripheral blood and a fresh semen sample. Both patients had none of the STS deleted in the peripheral blood DNA. Y chromosome microdeletion analysis in the MDA amplified SRY-positive single sperm DNA confirmed the presence of the same deletion in all 10 sperm for one patient and eight out of 10 sperm in the second patient. CONCLUSIONS: Our observations suggest that some of the teratozoospermia might be related to gonadal mosaic Y chromosome microdeletions. Gonadal mosaicism can be a source of de novo transmissions of Y chromosome microdeletions. The application of MDA can yield enough DNA from a single sperm for genetic analyses.

Chromosome Deletion↗

PubMed2005

Clinical application of multiple displacement amplification in preimplantation genetic diagnosis.

Multiple displacement amplification (MDA) is a technique used in the amplification of very small amounts of DNA. MDA is reported to yield large quantities of high-quality DNA. The applicability of MDA to single cells was recently demonstrated as a potential technique for preimplantation genetic diagnosis (PGD). This paper shows the first clinical application of MDA in PGD. Two cycles of PGD were performed in two diseases, resulting in two pregnancies. All the diagnoses given on blastomeres were confirmed on the non-transferred whole embryos. The blastomere diagnosis was coupled with short tandem repeat (STR) analysis (16 loci) in all cycles. Allelic drop-out (ADO) assessment and amplification efficiency were evaluated on 40 single lymphocytes derived from parents of each disease. ADO and amplification failure were 10.3 and 2.2% for beta-thalassaemia and 17.9 and 2.2% for cystic fibrosis respectively. HLA matching for A, B and DR was performed successfully on single cell for the beta-thalassaemia family using similar methods to genomic DNA. The PGD protocol used in all diseases consists of MDA amplification, followed by a standard polymerase chain reaction protocol. Although HLA matching was not applied to embryos, its feasibility was shown on single cell DNA amplified by MDA. Altogether, these data show the simplicity and reliability of performing PGD in combination with HLA matching and STR analysis using MDA.

Cystic Fibrosis↗

PubMed2004

Preimplantation genetic diagnosis for Niemann-Pick disease type B.

BACKGROUND: Acid sphingomyelinase (ASM) deficient Niemann-Pick disease (NPD) is an autosomal recessive disorder caused by mutations in the ASM gene (SMPD1). More than 70 different mutations have been reported in this gene. NPD type B is the most common type in Saudi Arabia with a frequency of 1:40 000 to 1:100 000. The phenotype of Saudi Type B patients is more severe than patients reported from the West. Two mutations specific to Saudi patients have been inherited in the SMPD1 gene. Given the difficult management of the disease, we opted for a preventive approach to the suffering families by screening the whole SMPD1 gene for mutations followed by Preimplantation Genetic Diagnosis (PGD). METHODS: The family suffering from NPD-B underwent mutation screening for the entire SMPD1 gene followed by PGD using nested PCR and sequencing. RESULTS: A novel mutation in a family suffering from the same severe NPD-B phenotype is described in this report (W533R). After PGD, a singleton pregnancy ensued after transfer of one heterozygous and one normal embryo. Postnatal DNA testing of the newborn showed a normal homozygous genotype. CONCLUSIONS: This report reveals a new SMPD1 mutation responsible for similar Saudi severe phenotype, and the prevention of this disorder by PGD.

Adult↗

PubMed2004

Androgens and postmeiotic germ cells regulate claudin-11 expression in rat Sertoli cells.

In the present study we investigated whether fetal exposure to flutamide affected messenger and protein levels of claudin-11, a key Sertoli cell factor in the establishment of the hemotesticular barrier, at the time of two key events of postnatal testis development: 1) before puberty (postnatal d 14) during the establishment of the hemotesticular barrier, and 2) at the adult age (postnatal d 90) at the time of full spermatogenesis. The data obtained show that claudin-11 expression was inhibited in prepubertal rat testes exposed in utero to 2 and 10 mg/kg x d flutamide. However, in adult testes, the inhibition was observed only with 2, and not with 10, mg/kg x d of the antiandrogen. It is shown here that these differences between prepubertal and adult testes could be related to dual and opposed regulation of claudin-11 expression resulting from positive control by androgens and an inhibitory effect of postmeiotic germ cells. Indeed, testosterone is shown to stimulate claudin-11 expression in cultured Sertoli cells in a dose- and time-dependent manner (maximum effect with 0.06 microm after 72 h of treatment). In contrast, postmeiotic germ cells potentially exert a negative effect on claudin-11 expression, because adult rat testes depleted in spermatids (after local irradiation) displayed increased claudin-11 expression, whereas in a model of cocultured Sertoli and germ cells, spermatids, but not spermatocytes, inhibited claudin-11 expression. The apparent absence of claudin-11 expression changes in adult rat testes exposed to 10 mg/kg x d flutamide therefore could result from the antagonistic effects of 1) the inhibitory action of the antiandrogen and 2) the stimulatory effect of the apoptotic germ cells on claudin-11 expression. Together, due to the key role of claudin-11 in the hemotesticular barrier, the present findings suggest that such regulatory mechanisms may potentially affect this barrier (re)modeling during spermatogenesis.

Androgens↗

PubMed2004

Multiple displacement amplification on single cell and possible PGD applications.

Multiple displacement amplification (MDA) is a technique used in the amplification of very low amounts of DNA and reported to yield large quantities of high-quality DNA. We used MDA to amplify the whole genome directly from a single cell. The most common techniques used in PGD are PCR and fluorescent in-situ hybridization (FISH). There are many limitations to these techniques including, the number of chromosomes diagnosed for FISH or the quality of DNA issued from a single cell PCR. This report shows, for the first time, use of MDA for single cell whole genome amplification. A total of 16 short tandem repeats (STRs) were amplified successfully with a similar pattern to the genomic DNA. Furthermore, allelic drop out (ADO) derived from MDA was assessed in 40 single cells by analysing (i) heterozygosity for a known beta globin mutation (IVSI-5 C-G) and by studying (ii) the heterozygous loci present in the STRs. ADO turned out to be 10.25% for the beta globin gene sequencing and 5% for the fluorescent PCR analysis of STRs. Moreover, the amplification accuracy of MDA permitted the detection of trisomy 21 on a single cell using comparative genome hybridization-array. Altogether, these data suggest that MDA can be used for single cell molecular karyotyping and the diagnosis of any single gene disorder in PGD.

Alleles↗

PubMed2004

Pregnancy after preimplantation genetic diagnosis for Sanjad-Sakati syndrome.

Sanjad-Sakati syndrome (SSS) is an autosomal recessive disorder characterized by congenital hypoparathyroidism, growth and mental retardation. In Saudi Arabia, the disease is caused by a deletion of 12 bp (155-166nt) in the tubulin-specific chaperone E gene. In a family with two affected siblings with SSS, preimplantation genetic diagnosis (PGD) was performed. Fluorescent PCR (F-PCR) was utilized to check the heterozygosity and the homozygosity status of the parents and the affected children, respectively. F-PCR was then optimized for single-cell analysis by using peripheral blood lymphocytes. The patient underwent a cycle with intra-cytoplasmic sperm injection. A total of 11 embryos were obtained and biopsied. There were five heterozygous, three homozygous affected and three normal embryos. One heterozygous and one normal embryo were transferred because of their very good quality (morula). A singleton pregnancy was obtained, and amniosynthesis confirmed the presence of the heterozygous fetus. These results show for the first time, the feasibility of PGD for SSS.

DNA↗

PubMed2002

Deficiency in the repair of UV-induced DNA damage in human skin fibroblasts compromised for the ATM gene.

Ataxia-telangiectasia (A-T), is an autosomal recessive disease characterized by neurological and immunological symptoms, radiosensitivity and cancer predisposition. A-T cells exhibit a greatly decreased survival and a reduction in DNA synthesis inhibition as well as p53 induction in response to ionizing radiation. Occasionally, some strains of A-T cells have been reported to manifest a slightly enhanced sensitivity with no consistent observations of a deficiency in either cell cycle control or the repair of DNA damage after treatment with ultraviolet (UV) light. In the present study it is shown that skin fibroblasts from four A-T patients, compared with the control, display enhanced sensitivity to the killing effect of UV-light, moderate radioresistant DNA synthesis, and a reduction in viral recovery in the host cell reactivation (HCR) assay. PCR based analysis indicated that three of these UV-sensitive A-T cell strains bear a large deletion in the ATM gene, and no ATM polypeptide was detected in their cell free extracts. Moreover, it is shown that, in non-replicative conditions, these A-T cells are less efficient than normal cells in repairing the T4 endonuclease V sensitive sites. These results constitute the first clear evidence showing the deficiency of A-T cells in the repair of UV-induced DNA damage, and provide further information on the relationship between cell cycle control and DNA repair in human cells.

Ataxia Telangiectasia↗

PubMed2002

Pregnancy after preimplantation genetic diagnosis for Ataxia Telangiectasia.

Ataxia Telangiectasia (AT) is an autosomal recessive disorder with an incidence estimated at 1 in 40 000 to 1 in 100 000 live births. More than 100 different somatic and germ-line mutations have been identified in the AT gene, the majority of which cause premature protein truncation. The immense size of the AT gene (66 exons) complicates the detection of mutations. A Saudi family with three affected children suffering from AT consulted our IVF centre for preimplantation genetic diagnosis (PGD). Despite advanced maternal age and unknown mutation, the family was screened for AT mutations. A large deletion in the gene was found to be responsible for the phenotype of AT. The mutation detection permitted us to perform PGD on AT for the first time. Single cell PCR consisted of amplifying one of the deleted exons, exon 19. Homozygous affected embryos show an absence of the exon, while in heterozygous or normal embryos the exon is amplified successfully. After ICSI, three embryos were suitable for embryo biopsy. After biopsy only one embryo showed exon amplification and was transferred. A singleton pregnancy ensued and prenatal diagnosis confirmed the presence of exon 19. This report demonstrates that PGD is feasible despite advanced maternal age and poor response to follicle stimulation.

Adolescent↗

PubMedDate not supplied

Nucleolar precursor body distribution in pronuclei is correlated to chromosomal abnormalities in embryos.

In-vitro generated human embryos have low implantation rates and high chromosomal abnormalities. Embryos are mostly selected on the basis of microscopic morphological examination. The relationship between pronuclear morphology and chromosomal abnormalities was investigated in this study. Zygotes were scored according to pronuclear morphology on day 1. Excess embryos that were not transferred or cryopreserved on day 3 were fixed. Chromosomes 13, 18, 21, X and Y were analysed by fluorescence in-situ hybridization (FISH). A total of 125 embryos were analysed; 58 (46%) were abnormal, 32 (26%) were mosaic and 35 (28%) were normal. Results were analysed according to different pronuclear morphology. Zygotes with polarized pattern had a significantly lower incidence of chromosome abnormality than those with a non-polarized pattern. The presence of cytoplasmic halo, the size of each pronucleus and the number of nucleolar precursor body had no significant effect on chromosomal abnormalities. In conclusion, embryos generated from zygotes with polarized pattern have fewer chromosomal abnormalities compared with other patterns. A simple microscopic examination during fertilization confirmation would be useful to select embryos with fewer chromosomal abnormalities, preferably in combination with other observations shown to correlate with chromosomal abnormalities.

Adult↗