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Detection of Novel Gene Variants Associated with Congenital Hypothyroidism in a Finnish Patient Cohort

View Article: PubMed Central - PubMed

ABSTRACT

Background:: Congenital hypothyroidism (CH) is defined as the lack of thyroid hormones at birth. Mutations in at least 15 different genes have been associated with this disease. While up to 20% of CH cases are hereditary, the majority of cases are sporadic with unknown etiology. Apart from a monogenic pattern of inheritance, multigenic mechanisms have been suggested to play a role in CH. The genetics of CH has not been studied in Finland so far. Therefore, multigenic sequencing of CH candidate genes was performed in a Finnish patient cohort with both familial and sporadic CH.

Methods:: A targeted next-generation sequencing (NGS) panel, covering all exons of the major CH genes, was applied for 15 patients with sporadic and 11 index cases with familial CH.

Results:: Among the familial cases, six pathogenic mutations were found in the TPO, PAX8, and TSHR genes. Furthermore, pathogenic NKX2.1 and TG mutations were identified from sporadic cases, together with likely pathogenic variants in the TG, NKX2.5, SLC26A4, and DUOX2 genes. All identified novel pathogenic mutations were confirmed by Sanger-sequencing and characterized in silico and/or in vitro.

Conclusion:: In summary, the CH panel provides an efficient, cost-effective, and multigenic screening tool for both known and novel CH gene mutations. Hence, it may be a useful method to identify accurately the genetic etiology for dyshormogenic, familial, or syndromic forms of CH.

No MeSH data available.


Related in: MedlinePlus

Modified pedigrees and identified mutations of the familial congenital hypothyroidism (CH) cases with genetic and clinical data. The results of the thyroid function tests and thyroid size are aligned below. The reference values of umbilical blood thyrotropin (uTSH), and thyrotropin (TSH) and free thyroxine (fT4) serum hormone levels at three days of age or the time of diagnosis are included. Black, affected patients with CH; symbols with midline, asymptomatic heterozygous carriers; gray, adult onset hypothyroidism; white, no thyroid disease. Lined box (case 5) indicates the TPO R438H mutation. Serum thyroglobulin (TG) levels were measured at the time of enrollment into the study. The age (years) at time of diagnosis (0 = at birth) is shown. Thyroid size evaluated by thyroid ultrasound if data available (n, normal thyroid size and location; +, goiter; a, athyreosis/no thyroid gland not detected; h, hypoplastic or small thyroid; n*, no clinical signs of goiter during follow-up; #, no DNA available). The detailed clinical information of the families is described in the Supplementary Materials and Methods. NA, data not available. aPatient had mild hypotonia, delay of development (speech and motor development) and abnormal hearing response, babnormal hearing, cborn in week 29 + 3, or drenal agenesis.
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f1: Modified pedigrees and identified mutations of the familial congenital hypothyroidism (CH) cases with genetic and clinical data. The results of the thyroid function tests and thyroid size are aligned below. The reference values of umbilical blood thyrotropin (uTSH), and thyrotropin (TSH) and free thyroxine (fT4) serum hormone levels at three days of age or the time of diagnosis are included. Black, affected patients with CH; symbols with midline, asymptomatic heterozygous carriers; gray, adult onset hypothyroidism; white, no thyroid disease. Lined box (case 5) indicates the TPO R438H mutation. Serum thyroglobulin (TG) levels were measured at the time of enrollment into the study. The age (years) at time of diagnosis (0 = at birth) is shown. Thyroid size evaluated by thyroid ultrasound if data available (n, normal thyroid size and location; +, goiter; a, athyreosis/no thyroid gland not detected; h, hypoplastic or small thyroid; n*, no clinical signs of goiter during follow-up; #, no DNA available). The detailed clinical information of the families is described in the Supplementary Materials and Methods. NA, data not available. aPatient had mild hypotonia, delay of development (speech and motor development) and abnormal hearing response, babnormal hearing, cborn in week 29 + 3, or drenal agenesis.

Mentions: The diagnosis of permanent CH was based on TSH and T4 screening test at birth and confirmation test results at two to three years of age after cessation of T4 treatment temporarily. CH screening in Finland is based on the measurement of TSH levels from umbilical serum at birth. Where an abnormal (TSH >40 mIU/L) result is found, serum T4 is determined from the same sample, and a confirmation sample (for both TSH and T4) is taken when the newborn is 72 hours old. This screening leads to an early start to therapy and has a low rate of false-positive cases (10). Iodine uptake or iodine accumulation tests were not performed routinely. Serum thyroglobulin (TG) levels at the time of recruitment were measured by commercial ELISA (Novatec, Baltimore, MD). DNA from whole-blood samples was isolated with a kit (Qiagen, Valencia, CA). A total of 34 DNA samples were sequenced using the targeted NGS panel containing the genes listed in Table 1. The cohort included both cases with thyroid dysgenesis and dyshormogenesis. The other 17 DNA samples were obtained from sporadic cases, including 15 cases with permanent CH and two with hyperthyrotropinemia. Analyses included four CH patients with five known mutations in different genes responsible for CH (Supplementary Table S1; Supplementary Data are available online at www.liebertpub.com/thy). Eleven CH samples were index cases from unrelated families with at least two affected family members. The summary of the clinical data is described in Figure 1 and in further detail in the supplementary section (Supplementary Materials and Methods).


Detection of Novel Gene Variants Associated with Congenital Hypothyroidism in a Finnish Patient Cohort
Modified pedigrees and identified mutations of the familial congenital hypothyroidism (CH) cases with genetic and clinical data. The results of the thyroid function tests and thyroid size are aligned below. The reference values of umbilical blood thyrotropin (uTSH), and thyrotropin (TSH) and free thyroxine (fT4) serum hormone levels at three days of age or the time of diagnosis are included. Black, affected patients with CH; symbols with midline, asymptomatic heterozygous carriers; gray, adult onset hypothyroidism; white, no thyroid disease. Lined box (case 5) indicates the TPO R438H mutation. Serum thyroglobulin (TG) levels were measured at the time of enrollment into the study. The age (years) at time of diagnosis (0 = at birth) is shown. Thyroid size evaluated by thyroid ultrasound if data available (n, normal thyroid size and location; +, goiter; a, athyreosis/no thyroid gland not detected; h, hypoplastic or small thyroid; n*, no clinical signs of goiter during follow-up; #, no DNA available). The detailed clinical information of the families is described in the Supplementary Materials and Methods. NA, data not available. aPatient had mild hypotonia, delay of development (speech and motor development) and abnormal hearing response, babnormal hearing, cborn in week 29 + 3, or drenal agenesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036323&req=5

f1: Modified pedigrees and identified mutations of the familial congenital hypothyroidism (CH) cases with genetic and clinical data. The results of the thyroid function tests and thyroid size are aligned below. The reference values of umbilical blood thyrotropin (uTSH), and thyrotropin (TSH) and free thyroxine (fT4) serum hormone levels at three days of age or the time of diagnosis are included. Black, affected patients with CH; symbols with midline, asymptomatic heterozygous carriers; gray, adult onset hypothyroidism; white, no thyroid disease. Lined box (case 5) indicates the TPO R438H mutation. Serum thyroglobulin (TG) levels were measured at the time of enrollment into the study. The age (years) at time of diagnosis (0 = at birth) is shown. Thyroid size evaluated by thyroid ultrasound if data available (n, normal thyroid size and location; +, goiter; a, athyreosis/no thyroid gland not detected; h, hypoplastic or small thyroid; n*, no clinical signs of goiter during follow-up; #, no DNA available). The detailed clinical information of the families is described in the Supplementary Materials and Methods. NA, data not available. aPatient had mild hypotonia, delay of development (speech and motor development) and abnormal hearing response, babnormal hearing, cborn in week 29 + 3, or drenal agenesis.
Mentions: The diagnosis of permanent CH was based on TSH and T4 screening test at birth and confirmation test results at two to three years of age after cessation of T4 treatment temporarily. CH screening in Finland is based on the measurement of TSH levels from umbilical serum at birth. Where an abnormal (TSH >40 mIU/L) result is found, serum T4 is determined from the same sample, and a confirmation sample (for both TSH and T4) is taken when the newborn is 72 hours old. This screening leads to an early start to therapy and has a low rate of false-positive cases (10). Iodine uptake or iodine accumulation tests were not performed routinely. Serum thyroglobulin (TG) levels at the time of recruitment were measured by commercial ELISA (Novatec, Baltimore, MD). DNA from whole-blood samples was isolated with a kit (Qiagen, Valencia, CA). A total of 34 DNA samples were sequenced using the targeted NGS panel containing the genes listed in Table 1. The cohort included both cases with thyroid dysgenesis and dyshormogenesis. The other 17 DNA samples were obtained from sporadic cases, including 15 cases with permanent CH and two with hyperthyrotropinemia. Analyses included four CH patients with five known mutations in different genes responsible for CH (Supplementary Table S1; Supplementary Data are available online at www.liebertpub.com/thy). Eleven CH samples were index cases from unrelated families with at least two affected family members. The summary of the clinical data is described in Figure 1 and in further detail in the supplementary section (Supplementary Materials and Methods).

View Article: PubMed Central - PubMed

ABSTRACT

Background:: Congenital hypothyroidism (CH) is defined as the lack of thyroid hormones at birth. Mutations in at least 15 different genes have been associated with this disease. While up to 20% of CH cases are hereditary, the majority of cases are sporadic with unknown etiology. Apart from a monogenic pattern of inheritance, multigenic mechanisms have been suggested to play a role in CH. The genetics of CH has not been studied in Finland so far. Therefore, multigenic sequencing of CH candidate genes was performed in a Finnish patient cohort with both familial and sporadic CH.

Methods:: A targeted next-generation sequencing (NGS) panel, covering all exons of the major CH genes, was applied for 15 patients with sporadic and 11 index cases with familial CH.

Results:: Among the familial cases, six pathogenic mutations were found in the TPO, PAX8, and TSHR genes. Furthermore, pathogenic NKX2.1 and TG mutations were identified from sporadic cases, together with likely pathogenic variants in the TG, NKX2.5, SLC26A4, and DUOX2 genes. All identified novel pathogenic mutations were confirmed by Sanger-sequencing and characterized in silico and/or in vitro.

Conclusion:: In summary, the CH panel provides an efficient, cost-effective, and multigenic screening tool for both known and novel CH gene mutations. Hence, it may be a useful method to identify accurately the genetic etiology for dyshormogenic, familial, or syndromic forms of CH.

No MeSH data available.


Related in: MedlinePlus