A truncating TPO mutation (Y55X) in patients with hypothyroidism and total iodide organification defect.

UNLABELLED: Absract Purpose: Mutations in the TPO gene have been reported to cause congenital hypothyroidism (CH), and our aim in this study was to determine the genetic basis of congenital hypothyroidism in two affected children coming from a consanguineous family. METHODS: Since CH is usually inherited in autosomal recessive manner in consanguineous/multi case-families, we adopted a two-stage strategy of genetic linkage studies and targeted sequencing of the candidate genes. First we investigated the potential genetic linkage of the family to any known CH locus using microsatellite markers and then screened for mutations in linked-gene by Sanger sequencing. RESULTS: The family showed potential linkage to the TPO gene and we detected a non-sense mutation (Y55X) in both cases that had total iodode organification defect (TIOD). The mutation segregated with disease status in the family. Y55X is the only truncating mutation in the exon 2 of the TPO gene reported in the literature and results in the earliest stop codon known in the gene to date. CONCLUSIONS: This study confirms the pathogenicity of Y55X mutation and demonstrates that a nonsense mutation in the amino-terminal coding region of the TPO gene could totally abolish the function of the TPO enzyme leading to TIOD. Thus it helps to establish a strong genotype/phenotype correlation associated with this mutation. It also highlights the importance of molecular genetic studies in the definitive diagnosis and accurate classification of CH.

An epileptic case with mosaic ring chromosome 6 and 6q terminal deletion.

Ring chromosomes are rare chromosome disorders that arise usually de novo. Children with ring chromosome 6 have a wide range of intellectual functioning and congenital anomalies. We report an epileptic case of a 10-year-old boy to be mild psychomotor retardation and dysmorphic traits including microcephaly, brachycephaly, flat occiput, large and apparently low set ears, and bilateral syndactyly between his second and third fingers with mosaic ring chromosome 6 and 6q terminal deletion. Peripheral chromosome and fluorescent in situ hybridisation (FISH) analysis of the patient showed mos46,XY,r(6)(p24;q26),del(6)(q27) [30]/46,XY,del(6)(q27) [20] de novo. We presented the patient in the light of literature because the mosaic ring 6 and 6q terminal deletion was different caryotypically from other mosaic ring 6 patients.

Genetic diagnosis in infertile men with numerical and constitutional sperm abnormalities.

Infertile men having numerical or structural sperm defects may carry several genetic abnormalities (karyotype abnormalities, Y chromosome microdeletions, cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations, androgen receptor gene mutations, and abnormalities seen in sperm cells) leading to this situation. First we aimed to investigate the relationship between the numerical and constitutional (morphological) sperm anomalies and the genetic disorders that can be seen in infertile males. Our other aim was to compare two different kinds of kits that we use for the detection of Y chromosome microdeletions. Sixty-three infertile males [44 nonobstructive azoospermic, 8 severe oligozoospermic, and 11 oligoasthenoteratozoospermic] were investigated in terms of somatic chromosomal constitutions and microdeletions of the Y chromosome. Sperm aneuploidy levels were analyzed by fluorescence in situ hybridization (FISH) in sperm cells obtained from the semen of six OAT patients. Microdeletion and sex chromosome aneuploidy (47,XXY) rates in somatic cells were found to be approximately 3.2% and 4.7%, respectively. Sperm aneuploidy rates were determined as 9%, 22%, and 47% in three patients out of six. Two of these three patients also had high rates of head anomalies in semen samples. High correlation was found between sperm aneuploidy rates and sperm head anomalies. Since the introduction of the assisted reproductive techniques for the treatment of severe male infertility, genetic tests and genetic counseling became very important due to the transmission of genetic abnormalities to the next generation. Thus in a very near future, for a comprehensive male infertility panel, it will be essential to include additional genetic tests, such as CFTR gene mutations, sperm mitochondrial DNA mutations, and androgen receptor gene mutations, besides the conventional chromosomal analyses, Y chromosome microdeletion detection, and sperm-FISH analyses.

Short tandem repeats haplotyping of the HLA region in preimplantation HLA matching.

Recently, preimplantation genetic diagnosis (PGD) has been considered for several indications beyond its original purpose, not only to test embryos for genetic disease but also to select embryos for a nondisease trait, such as specific human leukocyte antigen (HLA) genotypes, related to immune compatibility with an existing affected child in need of a haematopoetic stem cell (HSC) transplant. We have optimized an indirect single-cell HLA typing protocol based on a multiplex fluorescent polymerase chain reaction (PCR) of short tandem repeat (STR) markers scattered throughout the HLA complex. The assay was clinically applied in 60 cycles from 45 couples. A conclusive HLA-matching diagnosis was achieved in 483/530 (91.1%) of the embryos tested. In total, 74 (15.3%) embryos revealed an HLA match with the affected siblings, 55 (11.4%) of which resulted unaffected and 46 (9.5%) have been transferred to the patients. Nine pregnancies were achieved, five healthy HLA-matched children have already been delivered and cord blood HSCs, were transplanted to three affected siblings, resulting in a successful haematopoietic reconstruction.

One Base Deletion (c.2422delT) in the TPO Gene Causes Severe Congenital Hypothyroidism.

OBJECTIVE: Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder and mutations in the TPO gene have been reported to cause CH. Our aim in this study was to determine the genetic basis of CH in two affected individuals coming from a consanguineous family. METHODS: Since CH is usually inherited in autosomal recessive manner in consanguineous/multi-case families, we adopted a two-stage strategy of genetic linkage studies and targeted sequencing of the candidate genes. First, we investigated the potential genetic linkage of the family to any known CH locus using microsatellite markers and then screened for mutations in linked-gene by Sanger sequencing. RESULTS: The family showed potential linkage to the TPO gene and we detected a deletion (c.2422delT) in both cases. The mutation segregated with disease status in the family. CONCLUSION: This study demonstrates that a single base deletion in the carboxyl-terminal coding region of the TPO gene could cause CH and helps to establish a genotype/phenotype correlation associated with the mutation. The study also highlights the importance of molecular genetic studies in the definitive diagnosis and accurate classification of CH.

Novel truncating thyroglobulin gene mutations associated with congenital hypothyroidism.

Mutations in the thyroglobulin (TG) gene have been reported to cause congenital hypothyroidism (CH) and we have been investigating the genetic architecture of CH in a large cohort of consanguineous/multi-case families. Our aim in this study was to determine the genetic basis of CH in four affected individuals coming from two separate consanguineous families. Since CH is usually inherited in autosomal recessive manner in consanguineous/multi-case families, we adopted a two-stage strategy of genetic linkage studies and targeted sequencing of the TG gene. First we investigated the potential genetic linkage of families to any known CH locus using microsatellite markers and then determined the pathogenic mutations in linked-genes by Sanger sequencing. Both families showed potential linkage to TG locus and we detected two previously unreported nonsense TG mutations (p.Q630X and p.W637X) that segregated with the disease status in both families. This study highlights the importance of molecular genetic studies in the definitive diagnosis and classification of CH, and also adds up to the limited number of nonsense TG mutations in the literature. It also suggests a new clinical testing strategy using next-generation sequencing in all primary CH cases.

An essential splice site mutation (c.317+1G>A) in the TSHR gene leads to severe thyroid dysgenesis.

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder and 2% of cases have familial origin. Our aim in this study was to determine the genetic alterations in two siblings with CH coming from a consanguineous family. Because CH is often inherited in autosomal recessive manner in consanguineous/multicase-families, we first performed genetic linkage studies to all known causative CH loci followed by conventional sequencing of the linked gene. The family showed potential linkage to the TSHR locus, and we detected an essential splice site mutation (c.317+1G>A) in both siblings. RT-PCR analysis confirmed the functionality of the mutation. The mutation was homozygous in the cases whereas heterozygous in carrier parents and an unaffected sibling. Here we conclude that thyroid agenesis in both siblings in this study originates from c.317+1G>A splice site mutation in the TSHR gene, and this study underlines the importance of detailed molecular genetic studies in the definitive diagnosis and classification of CH.

A nonsense thyrotropin receptor gene mutation (R609X) is associated with congenital hypothyroidism and heart defects.

Congenital hypothyroidism (CH), one of the most important preventable causes of mental retardation, is a clinical condition characterized by thyroid hormone deficiency in newborns. CH is most often caused by defects in thyroid development leading to thyroid dysgenesis. The thyroid-stimulating hormone receptor (TSHR) is the main known gene causing thyroid dysgenesis in consanguineous families with CH. In this study, we aim to determine the genetic alteration in a case with congenital hypothyroidism and heart defects coming from a consanguineous family. We utilized genetic linkage analysis and direct sequencing to achieve our aim. Our results revealed that the family showed linkage to the TSHR locus, and we detected a homozygous nonsense mutation (R609X) in the case. Apart from other cases with the same mutation, our case had accompanying cardiac malformations. Although cardiac malformations are not uncommon in sporadic congenital hypothyroidism, here, they are reported for the first time with R609X mutation in a familial case.

A truncating DUOX2 mutation (R434X) causes severe congenital hypothyroidism.

Mutations in DUOX2 have been reported to cause congenital hypothyroidism (CH), and our aim in this study was to determine the genetic basis of CH in two affected individuals coming from a consanguineous family. Because CH is usually inherited in autosomal recessive manner in consanguineous/multicase families, we adopted a two-stage strategy of genetic linkage studies and targeted sequencing of the candidate genes. First, we investigated the potential genetic linkage of the family to any known CH locus using microsatellite markers and then screened for mutations in linked genes by Sanger sequencing. The family showed potential linkage to DUOX2 locus and we detected a nonsense mutation (R434X) in both cases and the mutation segregated with disease status in the family. This study highlights the importance of molecular genetic studies in the definitive diagnosis and classification of CH, and it also suggests a new clinical testing strategy using next-generation sequencing in all primary CH cases.

A deletion including exon 2 of the TSHR gene is associated with thyroid dysgenesis and severe congenital hypothyroidism.

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder and 2% of cases have a familial origin. Our aim in this study was to determine the genetic alterations in two siblings with CH coming from a consanguineous family. As CH is often inherited in an autosomal recessive manner in consanguineous/multi case-families, we first performed genetic linkage studies to all known causative CH loci followed by conventional sequencing of the linked gene. The family showed potential linkage to the TSHR locus and our attempts to amplify and sequence exon 2 of the TSHR gene continuously failed. Subsequent RT-PCR analysis using mRNA and corresponding cDNA showed a large deletion including the exon 2 of the gene. The deletion was homozygous in affected cases whilst heterozygous in carrier parents. Here we conclude that CH in both siblings of this study originates from a large deletion including the exon 2 of the TSHR gene. This study demonstrates that full sequence analysis in a candidate CH gene might not always be enough to detect genetic alterations, and additional analyses such as RT-PCR and MLPA might be necessary to describe putative genetic causes of the disease in some cases. It also underlines the importance of detailed molecular genetic studies in the definitive diagnosis and classification of CH.

Preimplantation genetic diagnosis (PGD) for extremes--successful birth after PGD for a consanguineous couple carrying an identical balanced reciprocal translocation.

OBJECTIVE: To report a healthy birth after preimplantation genetic diagnosis (PGD) performed for a consanguineous couple carrying an identical familial reciprocal translocation in both partners. DESIGN: Case report. SETTING: In vitro fertilization (IVF) clinic and genetic laboratory in a private hospital. PATIENT(S): Consanguineous couple carrying the same balanced reciprocal translocation: 46,XX,t(1;16)(q12;q11.2) and 46,XY,t(1;16)(q12;q11.2). INTERVENTION(S): 25 oocyte-cumulus complexes were retrieved 36 hours after human chorionic gonadotropin injection; metaphase II oocytes were fertilized by intracytoplasmic sperm injection; single blastomere biopsy was performed on 15 embryos on day 3; one embryo was found to be normal or balanced according to fluorescent in situ hybridization studies, embryo transfer was performed on day 4. MAIN OUTCOME MEASURE(S): Healthy birth of homozygous double translocation carrier twins with 46,XY,t(1;16)(q12;q11.2)mat,t(1;16)(q12;q11.2)pat karyotype. RESULT(S): Healthy monozygotic male twins were born at 36 weeks of gestation. Karyotype studies of the babies revealed that they are double translocation homozygotes: 46,XY,t(1;16)(q12;q11.2)mat,t(1;16)(q12;q11.2)pat. They are healthy and more than 4 years old later show no physical or mental abnormalities. CONCLUSION(S): To our knowledge, this is the first PGD study performed for a couple who carry the same reciprocal translocation. The twins born after this study are rare examples in the literature of healthy balanced reciprocal translocation homozygotes.