A novel PITX2 mutation in non-syndromic orodental anomalies

OBJECTIVE

To identify orodental characteristics and genetic aetiology of a family affected with non-syndromic orodental anomalies.

SUBJECTS AND METHODS

Physical and oral features were characterised. DNA was collected from an affected Thai family. Whole-exome sequencing was employed to identify the pathogenic variants associated with inherited orodental anomalies. The presence of the identified mutation was confirmed by Sanger sequencing.

RESULTS

We observed unique orodental manifestations including oligodontia, retained primary teeth, taurodont molars, peg-shaped maxillary central incisors, high attached frenum with nodule and midline diastema in the proband and her mother. Mutation analyses revealed a novel heterozygous frameshift deletion, c.573_574delCA, p.L193QfsX5, in exon 5 of PITX2A in affected family members. The amino acid alterations, localised in the transcriptional activation domain 2 in the C-terminus of PITX2, were evolutionarily conserved. Mutations in PITX2 have been associated with autosomal-dominant Axenfeld-Rieger syndrome and non-syndromic eye abnormalities, but never been found to cause isolated oral anomalies.

CONCLUSIONS

This study for the first time demonstrates that the PITX2 mutation could lead to non-syndromic orodental anomalies in humans. We propose that the specific location in the C-terminal domain of PITX2 is exclusively necessary for tooth development.

A novel GJA1 mutation in oculodentodigital dysplasia with extensive loss of enamel

OBJECTIVE

To characterize clinical features and identify genetic causes of a patient with oculodentodigital dysplasia (ODDD).

SUBJECTS AND METHODS

Clinical, dental, radiological features were obtained. DNA was collected from an affected Thai family. Whole-exome sequencing was employed to identify the disease-causing mutation causing ODDD. The presence of the identified variant was confirmed by Sanger sequencing.

RESULTS

The proband suffered with extensive enamel hypoplasia, polysyndactyly and clinodactyly of the 3rd-5th fingers, microphthalmia, and unique facial characteristics of ODDD. Mutation analysis revealed a novel missense mutation, c. 31C>A, p.L11I, in the GJA1 gene which encodes gap junction channel protein connexin 43. Bioinformatics and structural modeling suggested the mutation to be pathogenic. The parents did not harbor the mutation.

CONCLUSIONS

This study identified a novel de novo mutation in the GJA1 gene associated with severe tooth defects. These results expand the mutation spectrum and understanding of pathologic dental phenotypes related to ODDD.

Interleukin-10 promoter polymorphisms and expression in Thai children with juvenile systemic lupus erythematosus

Interleukin (IL)-10 expression is regulated by its promoter and correlated with the activity of adult-onset lupus (systemic lupus erythematosus (SLE)). As the pathogenesis of adult-onset SLE may differ from SLE with the age at onset <18 years old (juvenile SLE or JSLE), we evaluated polymorphisms at positions −1082A/G, −819T/C and −592A/C of the IL-10 promoter and serum IL-10 levels in 71 patients with JSLE. Disease activity was determined by the SLE disease activity index (SLEDAI). Active SLE was defined by SLEDAI ≥6 and inactive SLE was defined by SLEDAI equal to zero. The mean age was 14.5 ± 2.8 years. Nephritis occurred in 57 patients. In JSLE patients, −592 CC and −819 CC were identified with a higher frequency than in controls with the odds ratio (OR) of 2.75 (95% confidence interval (CI) 1.11–6.81, p = 0.04). GCC increased the susceptibility to nephritis in patients with JSLE (OR 2.16, 95% CI 1.07–4.35, p = 0.03). Serum IL-10 levels were significantly higher in 20 JSLE patients with active disease than in 27 patients with inactive disease and in 15 healthy children ( p < 0.001). In conclusion, IL-10 expression was upregulated in active JSLE. The −819 CC and −592 CC genotypes increased the susceptibility to JSLE and GCC increased the susceptibility to nephritis.

Pathogenic mechanism of mutations in the thyroid hormone receptor β gene

BACKGROUND

Resistance to thyroid hormone (RTH) is characterized by a variable degree of reduced tissue sensitivity to thyroid hormone (TH). It is usually caused by mutations in the TH receptor-β (TRβ) gene.

AIMS

To characterize clinical and molecular features of a Thai patient with RTH. Functional significance of the identified mutation as well as other uncharacterized TRβ mutations was also investigated.

MATERIALS AND METHODS

Exons 3-10 of the TRβ gene were assessed by PCR-sequencing. Functional characterization of the mutant TRβ was determined by the luciferase reporter system.

RESULTS

A mutation in exon 9 of the TRβ gene resulting in a methionine to threonine substitution at codon 313 was identified. The functional consequence of this mutation and other uncharacterized known mutations (p.I276L, p.I280S, p.L330S, p.G344A, p.M442T) was evaluated by transfection studies. Four out of 6 had a significant impairment of T3-dependent transactivation. When co-transfected with the wild-type TRβ, all exhibited a dominant negative effect.

CONCLUSION

A de novo mutation was identified in the patient with clinical diagnosis of RTH. Our findings provide a strong support that interfering with the T3-mediated transcriptional activation of the wild-type TRβ independent of the ability to activate transcription is a major pathogenic mechanism causing RTH.

Association of CD247 with systemic lupus erythematosus in Asian populations

OBJECTIVE

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. CD247 (CD3Z, TCRZ) plays a vital role in antigen recognition and signal transduction in antigen-specific immune responses, and is known to be involved in SLE pathogenesis. Weak disease association was reported for genetic variants in this gene in Caucasian studies for SLE, Crohn's disease and systemic sclerosis, but its role as a genetic risk factor was never firmly established.

METHODS

In this study, using a collection of 612 SLE patients and 2193 controls of Chinese ethnicity living in Hong Kong in a genome-wide study, single nucleotide polymorphisms (SNPs) in and around CD247 were identified as being associated with SLE. The two most significant SNPs in this locus were selected for further replication using TaqMan genotyping assay in 3339 Asian patients from Hong Kong, Mainland China, and Thailand, as well as 4737 ethnically and geographically matched controls.

RESULTS

The association of CD247 with SLE in Asian populations was confirmed (rs704853: odds ratio [OR] = 0. 81, p = 2.47 × 10(-7); rs858543: OR = 1.10, p = 0.0048). Patient-only analysis suggested that rs704853 is also linked to oral ulcers, hematologic disorders and anti-double-stranded DNA (dsDNA) antibody production.

CONCLUSION

A significant association between variants in CD247 and SLE was demonstrated in Asian populations. Understanding the involvement of CD247 in SLE may shed new light on disease mechanisms and development of new treatment paradigms.

Prenatal diagnosis of a novel mutation, c.529C>T (p.Q177X), in the BCKDHA gene in a family with maple syrup urine disease

Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder caused by defective activity of the branched-chain alpha-keto-acid dehydrogenase (BCKD) complex. The disease-causing mutations can affect the BCKDHA, BCKDHB or DBT genes encoding for the E1a, E1b, and E2 subunits, respectively, of the BCKD complex. Here we report a girl who first presented to our clinic at 4 years of age with profound mental retardation. A diagnosis of MSUD was subsequently made based on the results of plasma amino acid analysis. Mutation analysis confirmed that she was homozygous for a novel mutation, c.529C>T (p.Q177X) in BCKDHA, while both parents, who were first cousins, were heterozygous. This enabled us to give an option of prenatal diagnosis to the parents. The prenatal testing for MSUD was performed during the mother's subsequent pregnancy and revealed that the fetus was heterozygous for the mutation. The healthy male neonate was born and his genotype was tested by restriction enzyme analysis, which confirmed the result of the prenatal testing. In summary, a late diagnosis of MSUD in patients without an unusual odour could occur especially in countries without neonatal screening programs as seen in the index patient. Mutation detection was, however, still beneficial to the family since prenatal testing could be performed in subsequent pregnancies. In addition, a novel mutation was found, expanding the mutation spectrum of this disease.

TBX22 mutations are a frequent cause of non-syndromic cleft palate in the Thai population

Mutations in the TBX22 gene underlie an X-linked malformation syndrome with cleft palate (CP) and ankyloglossia. Its mutations also result in non-syndromic CP in some populations. To investigate whether mutations in TBX22 play a part in the formation of non-syndromic CP in the Thai population, we performed mutation analysis covering all the coding regions of the TBX22 gene in 53 unrelated Thai patients with non-syndromic CP. We identified four potentially pathogenic mutations, 359G-->A (R120Q), 452G-->T (R151L), 1166C-->A (P389Q), and 1252delG in four different patients. All mutations were not detected in at least 112 unaffected ethnic-matched control chromosomes and had never been previously reported. R120Q and R151L, found in two sporadic cases, were located in the DNA binding T-box domain. P389Q and 1252delG, found in two familial cases, were at the carboxy-terminal region, which has never been described. Our study indicates that TBX22 mutations are responsible for a significant proportion of Thai non-syndromic CP cases confirming its importance as a frequent cause of non-syndromic CP across different populations.

Expanding the phenotypic spectrum of Caffey disease

Infantile cortical hyperostosis (ICH) is an inherited disorder characterized by hyperirritability, acute inflammation of soft tissues, and massive subperiosteal new bone formation. It typically appears in early infancy and is considered a benign self-limiting disease. We report a three-generation Thai family with ICH, the oldest being a 75-year-old man. A heterozygous mutation for a 3040C-->T in exon 41 of COL1A1 was found in affected individuals, further confirming the autosomal dominance of Caffey disease that is caused by this particular mutation. The novel findings in our studies include short stature and persistent bony deformities in the elderly. The height mean Z-score of the five affected individuals was -1.75, compared to 0.53 of the other seven unaffected individuals giving a p-value of 0.008. Short stature may be partly due to progressive height loss from scoliosis, compression fractures of the spine and genu varus. These features, which have not previously been described, expand the phenotypic spectrum of the Caffey disease.