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| Author(s): |
Renata da Cunha Scalco
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2015-09-04 |
| Examining board members: |
Alexander Augusto de Lima Jorge;
Milena Gurgel Teles Bezerra;
Andrea Glezer;
Magnus Régios Dias da Silva
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| Advisor: | Alexander Augusto de Lima Jorge |
| Abstract | |
Homozygous inactivating mutations in signal transducer and activator of transcription 5B gene (STAT5B) cause growth hormone insensitivity associated with signs of severe immune dysfunction, such as recurrent infections, lymphoid interstitial pneumonia and other autoimmune events. The phenotypic characterization of these mutations in heterozygous state has not been accomplished previously. Two patients with a homozygous STAT5B mutation (c.424_427del / p.L142RfsX19) are Brazilian brothers born in the city of Criciúma, Santa Catarina, and there is not known consanguinity in their family. Moreover, there was a report about two similar cases in this city, already deceased, suggesting that STAT5B mutations could be relatively frequent in this region. The objectives of this study were to evaluate the frequency of STAT5B c.424_427del mutation in Criciúma, to assess the existence of the founder effect and to characterize the effect of heterozygous STAT5B c.424_427del mutation on anthropometric and hormonal phenotypes. To evaluate the frequency of this mutation in Criciúma, 1192 individuals from the population were genotyped. Seven heterozygous individuals were identified, which characterized a minimum allele frequency of 0.29% (95% confidence interval: 0.08 to 0.5%), significantly higher than the frequency of other pathogenic variants described in public databases. By using the Hardy-Weinberg law, it was possible to estimate the incidence of cases of individuals homozygous for this mutation at one every 40 years. However, by using the highest possible frequency according to the confidence interval, this incidence could reach one every 13 years. Additionally, the parents of the two reported cases who were similar to patients with homozygous STAT5B mutations were genotyped and these parents were heterozygous for STAT5B c.424_427del mutation. To assess the founder effect, two markers near the mutation were analyzed in the two boys homozygous for STAT5B c.424_427del mutation, in 33 heterozygous individuals from seven unrelated families and in 53 control individuals. The same haplotype was present in the homozygous boys and in all heterozygous individuals, while in only 9,4% control individuals (p < 0,001), pointing to the probability that STAT5B c.424_427del mutation in different families has been inherited from a common ancestor. To study the effects of heterozygous STAT5B c.424_427del mutation, 33 heterozygous individuals were compared to 38 non-carrier relatives on height and some laboratorial tests. Heterozygous individuals were significantly shorter than their noncarrier relatives, with a height reduction of 0.6 standard deviation scores (p= 0,006). Furthermore, they had a significant reduction in insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP-3) standard deviation scores, without differences in the other exams. These findings show that heterozygous STAT5B mutations cause a significant negative impact on height, milder than the effect seen in patients with homozygous mutations, with height within the normal range. This result favors the hypothesis that rare pathogenic variants in heterozygous state contribute to normal height variability (AU) | |
| FAPESP's process: | 11/15078-0 - Study of the phenotype associated to heterozigous STAT5B mutation p.L142fsX161 |
| Grantee: | Renata da Cunha Scalco Tirapeli |
| Support Opportunities: | Scholarships in Brazil - Doctorate (Direct) |