RESUMEN
The present report studies a large kindred (WR) with generalized thyroid hormone resistance that has varying degrees of neuropsychological dysfunction, hyperactivity, poor attention span, decreased IQ and/or abnormalities in spatial perception. In this kindred, there has been found tight linkage of the syndrome with the c-erb A beta gene. The present study was performed to identify the presence of a possible gene mutation as a cause for this syndrome. DNA from peripheral leukocytes was isolated from 15 unaffected and 8 affected individuals from the kindred. Primers encompassing exons 9 (nucleotides 1171-1429) and 10 (nucleotides 1430-1698) were synthesized and used in PCR reactions to amplify these exons. Direct sequencing revealed a consistent substitution in each affected subject, but in none of the unaffected individuals, of a C to T change in one allele from nucleotide 1243, resulting in an arg to cys change in codon 315. The mutant and wild-type human beta 1 receptors were prepared and their translated proteins were analyzed for T3 binding. The WR T3 receptor from affected patients had reduced T3 binding affinity, with values approximately 2.5 x 10(10) M-1 compared to about 5 x 10(10) M-1 in normals. In summary, we have: i) identified a consistent and reproducible mutation of a C to T change in nucleotide 1243 in each of the affected but in none of the unaffected individuals of a large well characterized kindred with generalized thyroid hormone resistance; and ii) noted that the WR allele causes an approximate 50% decrease in the T3 binding affinity.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Arginina/genética , Codón , Cistina/genética , Mutación , Proteínas Proto-Oncogénicas/genética , Receptores de Hormona Tiroidea/genética , Secuencia de Bases , ADN/química , Desoxirribonucleasas de Localización Especificada Tipo II , Resistencia a Medicamentos , Ligamiento Genético , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Polimorfismo de Longitud del Fragmento de Restricción , Receptores de Hormona Tiroidea/metabolismo , Síndrome , Hormonas Tiroideas , Triyodotironina/metabolismoRESUMEN
Human TSH receptor (hTSH-R) gene and RNA transcripts were analyzed by Southern and Northern blots in patients with various thyroid disorders, and in tissue cell lines. A 1.4 Kb cDNA encoding the extracellular human TSH-R domain was used as a probe. Southern analysis revealed two constant bands of 11.0 and 5.0 Kb (hTSH-R) in the thyroid and human white cell samples studied, regardless of the disease process. Northern analysis showed a predominant band at about 4.4 Kb in the thyroid tissues but not in non-thyroid tissue or cell lines tested. There were no gene rearrangements or abnormal transcripts in Graves' disease or multinodular goiter samples. In contrast, the labelled cDNA TSH-R probe did not bind to RNA isolated from 1 of 2 papillary cancer samples. A portion of the unique area of the h-TSH receptor (approximately nucleotides 1100-1230) was directly sequenced in thyroid glands from patients with Graves' disease, multinodular goiter, and differentiated thyroid cancer. No mutations or polymorphisms were identified in these samples, as compared to normal thyroid or control placenta, although further definition of sequence variation in other areas of the TSH receptor, as well as in more samples, needs to be performed. The present study indicates the normal patterns of DNA and RNA hybridization in a variety of thyroid tissues and disease states, and demonstrates that pathologic thyroid samples, with the possible exception of thyroid cancer, were not associated with specific nucleotide abnormalities in the unique area of the TSH receptor that was studied.
