scholarly journals Mutation screening of the thyroid peroxidase gene in a cohort of 55 Portuguese patients with congenital hypothyroidism

2005 ◽  
Vol 152 (2) ◽  
pp. 193-198 ◽  
Author(s):  
Carina Rodrigues ◽  
Paula Jorge ◽  
José Pires Soares ◽  
Isaura Santos ◽  
Regina Salomão ◽  
...  
Keyword(s):  
Congenital Hypothyroidism ◽  
Mutation Screening ◽  
Gene Mutations ◽  
Human Thyroid ◽  
Thyroid Peroxidase ◽  
Molecular Testing ◽  
Missense Mutations ◽  
Human Thyroid Peroxidase ◽  
Iodide Organification Defect ◽  
Organification Defect

Objective: Defects in the human thyroid peroxidase (TPO) gene are reported to be one of the causes of congenital hypothyroidism (CH) due to a total iodide organification defect. The aim of the present study was to determine the nature and frequency of TPO gene mutations in patients with CH, characterised by elevated TSH levels and orthotopic thyroid gland, identified in the Portuguese National Neonatal Screening Programme. Subjects and methods: The sample comprised 55 patients, from 53 unrelated families, with follow-up in the endocrinology clinics of the treatment centres of Porto and Lisbon. Mutation screening in the TPO gene (exons 1–17) was performed by single-strand conformational analysis followed by sequencing of fragments with abnormal migration patterns. Results: Eight different mutations were detected in 13 patients (seven homozygotes and six compound heterozygotes). Novel mutations included three missense mutations, namely 391T > C (S131P), 1274A > G (N425S) and 2512T > A (C838S), as well as the predictable splice mutation 2748G > A (Q916Q/spl?). The undocumented polymorphism 180-47A > C was also detected. Conclusion: The results are in accordance with previous observations confirming the genetic heterogeneity of TPO defects. The proportion of patients in which the aetiology was determined justifies the implementation of this molecular testing in our CH patients with dyshormonogenesis.

scholarly journals Two novel missense mutations in the thyroid peroxidase gene, R665W and G771R, result in a localization defect and cause congenital hypothyroidism

2002 ◽  
pp. 491-498 ◽  
Author(s):  
K Umeki ◽  
T Kotani ◽  
J Kawano ◽  
T Suganuma ◽  
I Yamamoto ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Congenital Hypothyroidism ◽  
Cellular Localization ◽  
Thyroid Peroxidase ◽  
Missense Mutations ◽  
Thyroid Hormone Biosynthesis ◽  
Thyroid Dyshormonogenesis ◽  
Hormone Biosynthesis ◽  
Iodide Organification Defect ◽  
Organification Defect

OBJECTIVE: Thyroid peroxidase (TPO) deficiency is one of the causes of thyroid dyshormonogenesis, because TPO plays a key role in thyroid hormone biosynthesis. To determine the frequency and pattern of TPO abnormalities, we have been screening TPO genes of patients with congenital goitrous hypothyroidism. SUBJECTS AND METHODS: TPO genes of a patient with congenital goitrous hypothyroidism and her parents were directly sequenced, and two novel missense mutations (R665W and G771R) were found. The former was derived from her father and the latter from her mother. R665 and G771 were well conserved in the peroxidase superfamily. When mRNAs containing each of the mutations were transfected into CHO-K1 cells, each cell showed faint TPO enzyme activity. However, immunofluorescence and immunoelectron microscopic analyses revealed that neither of the mutated TPOs reached the plasma membrane. CONCLUSIONS: Two novel missense mutations in the TPO gene were found. TPO proteins encoded by these mutated alleles showed abnormal cellular localization; namely, localization on the plasma membrane was disturbed. The loss of plasma membrane localization in mutated TPOs brought about the iodide organification defect, which was diagnosed as congenital hypothyroidism.

scholarly journals A novel mutation in the human thyroid peroxidase gene resulting in a total iodide organification defect

1999 ◽  
Vol 160 (2) ◽  
pp. 267-273 ◽  
Author(s):  
T Kotani ◽  
K Umeki ◽  
I Yamamoto ◽  
H Maesaka ◽  
K Tachibana ◽  
...  
Keyword(s):  
Northern Blot Analysis ◽  
Novel Mutation ◽  
Human Thyroid ◽  
Thyroid Peroxidase ◽  
Wild Type ◽  
Normal Thyroid ◽  
Mrna Transfection ◽  
Human Thyroid Peroxidase ◽  
Iodide Organification Defect ◽  
Organification Defect

In this study we describe a novel mutation of the thyroid peroxidase (TPO) gene that resulted in a total iodide organification defect. TPO activity and thyroxine formation in thyroglobulin in the thyroid gland of the patient were below the limits of detection. However, TPO mRNA was detectable at a similar size and concentration as compared with normal thyroid tissues when measured by Northern blot analysis. Sequence analysis of the TPO gene showed the presence of two mutations, a missense mutation in exon 7 and C insertion in exon 14. These mutations were heterozygous and located in different alleles. The latter mutation has already been reported as one of the mutations of the TPO gene resulting in total iodide organification defect. The former mutation was further analysed by mRNA transfection studies in which mutated mRNA was transfected to CHO-K1 cells by electroporation. The results of transfection studies showed that the cells transfected with mutated mRNA expressed similar size TPO molecules to those of cells transfected with wild-type mRNA but that they lacked TPO activity. The two mutations of the TPO gene resulting in the total iodide organification defect in the patient cosegregated from her parents.

Screening for mutations of the human thyroid peroxidase gene in patients with congenital hypothyroidism

2009 ◽  
Vol 104 (S 04) ◽  
pp. 121-123 ◽  
Author(s):  
A. Grüters ◽  
B. Köhler ◽  
A. Wolf ◽  
A. Söling ◽  
L. de Vijlder ◽  
...  
Keyword(s):  
Congenital Hypothyroidism ◽  
Human Thyroid ◽  
Thyroid Peroxidase ◽  
Peroxidase Gene ◽  
Human Thyroid Peroxidase

scholarly journals Two Different Mutations in the Thyroid Peroxidase Gene of a Large Inbred Amish Kindred: Power and Limits of Homozygosity Mapping1

1999 ◽  
Vol 84 (3) ◽  
pp. 1061-1071
Author(s):  
Silvana Pannain ◽  
Roy E. Weiss ◽  
Charles E. Jackson ◽  
Donald Dian ◽  
John C. Beck ◽  
...  
Keyword(s):  
Linkage Analysis ◽  
Family Members ◽  
Thyroid Peroxidase ◽  
Missense Mutations ◽  
Polymorphic Markers ◽  
Dna Pooling ◽  
Nuclear Families ◽  
A Genome ◽  
Iodide Organification Defect ◽  
Organification Defect

Approximately 10% of newborns with congenital hypothyroidism are unable to convert iodide into organic iodine. This iodide organification defect has a prevalence of 1 in 40,000 newborns and may be caused by defects in the thyroid peroxidase enzyme (TPO), the hydrogen peroxide-generating system, the TPO substrate thyroglobulin, or inhibitors of TPO. We identified a high incidence of severe hypothyroidism due to a complete iodide organification defect in the youngest generation of five nuclear families belonging to an inbred Amish kindred. Genealogical records permitted us to trace their origin to an ancestral couple 7–8 generations back and to identify an autosomal recessive pattern of inheritance. Initial studies of homozygosity by descent using two polymorphic markers within the TPO gene showed no linkage to the phenotype. In fact, 4 of 15 affected siblings from 2 of the nuclear families were heterozygous, resulting in homozygosity values of 73% and 53% in affected and unaffected family members, respectively. A genome-wide homozygosity screen using DNA pools from affected and unaffected family members localized the defect to a locus close to the TPO gene. Linkage analysis using 4 additional polymorphic markers within the TPO gene reduced the number of homozygous unaffected siblings to zero without altering the percent homozygosity initially found in the affected. Sequencing of the TPO gene revealed 2 missense mutations, E799K and R648Q. TPO 779K was found in both alleles of the 11 affected homozygotes, both mutations were present in each of the 3 affected compound heterozygotes, and there were no TPO mutations in 1 subject with hypothyroidism of different etiology. These results demonstrate the power of the DNA pooling strategy in the localization of a defective gene and the pitfalls of linkage analysis when 2 relatively rare mutations coexist in an inbred population.

Screening for mutations of the human thyroid peroxidase gene in patients with congenital hypothyroidism

1997 ◽  
Vol 49 (1) ◽  
pp. 76
Author(s):  
A. Gruters ◽  
B. Kohler ◽  
A. Wolf ◽  
A. Soling ◽  
L. De Vijider ◽  
...  
Keyword(s):  
Congenital Hypothyroidism ◽  
Human Thyroid ◽  
Thyroid Peroxidase ◽  
Peroxidase Gene ◽  
Human Thyroid Peroxidase
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