A functional alternative splicing mutation in AIRE gene causes autoimmune polyendocrine syndrome type 1

Aire Mutations and Autoimmune Diseases

Autoimmune diseases were first recognized by Mackay and Macfarlane Burnet in 1962 (Burnet and Mackay 1962). It is defined as the failure of an organism to tolerate its own cells and tissue, resulting in an aberrant immune response by lymphocytes (T-cell-driven disease) and/or antibodies (B-cell-driven disease). Autoimmune diseases can be divided into systemic autoimmune diseases and specific organ- or body-system diseases, including the endocrine, gastro-intestinal, and neurological systems, and it's not uncommon for individuals to experience multiple autoimmune conditions simultaneously. Autoimmune diseases affect ~10% of the population (Conrad et al. 2023), causing chronic suffering, vital organ failure, and premature death at the level of cancer and cardiovascular diseases. The rising incidence of these disorders poses a significant challenge to healthcare systems, underscoring the critical need to elucidate disease mechanisms and translate these into effective diagnostic tests and therapeutics. Current therapeutic strategies are predominantly confined to symptomatic relief through replacement therapy and broad-spectrum anti-inflammatory drugs, often resulting in increased disease burden, diminished life quality, and elevated mortality rates. Most autoimmune diseases are likely a result of a combination of different genetic and environmental factors. However, there are a few exemptions, like the autoimmune polyendocrine syndrome type 1 (APS-1) caused by mutations in the Autoimmune Regulator (AIRE) gene.

Transcriptome immune-regulatory differences between leprosy patients and type 1 reaction patients, before onset of symptoms

Leprosy is a chronic disease of the skin and peripheral nerves caused by Mycobacterium leprae. A major public health and clinical problem are leprosy reactions, which are inflammatory episodes that often contribute to nerve damage and disability. Type I reversal reactions (T1R) can occur after microbiological cure of leprosy and affect up to 50% of leprosy patients. Early intervention to prevent T1R and, hence, nerve damage, is a major focus of current leprosy control efforts. In a prospective study, we enrolled and collected samples from 32 leprosy patients before the onset of T1R. Whole blood aliquots were challenged with M. leprae sonicate or media and total RNA was extracted. After a three-year follow-up, the transcriptomic response was compared between cells from 22 patients who remained T1R-free and 10 patients who developed T1R during that period. Our analysis focused on differential transcript (i.e. isoform) expression and usage. Results showed that, at baseline, cells from T1R-destined and T1R-free subjects had no main difference in their transcripts expression and usage. However, the cells of T1R patients displayed a transcriptomic immune response to M. leprae antigens that was significantly different from the one of cells from leprosy patients who remained T1R-free. Transcripts with significantly higher upregulation in the T1R-destined group, compared to the cells from T1R-free patients, were enriched for pathways and GO terms involved in response to intracellular pathogens, apoptosis regulation and inflammatory processes. Similarly, transcript usage analysis pinpointed different transcript proportions in response to the in-vitro challenge of cells from T1R-destined patients. Hence, transcript usage in concert with transcript expression suggested a dysregulated inflammatory response including increased apoptosis regulation in the peripheral blood cells of T1R-destined patients before the onset of T1R symptoms. Combined, these results provided detailed insight into the pathogenesis of T1R.

A partial form of AIRE deficiency underlies a mild form of autoimmune polyendocrine syndrome type 1

Autoimmune polyendocrine syndrome type 1 (APS-1) is caused by mutations in the autoimmune regulator (AIRE) gene. Most patients present with severe chronic mucocutaneous candidiasis and organ-specific autoimmunity from early childhood, but the clinical picture is highly variable. AIRE is crucial for negative selection of T cells, and scrutiny of different patient mutations has previously highlighted many of its molecular mechanisms. In patients with a milder adult-onset phenotype sharing a mutation in the canonical donor splice site of intron 7 (c.879+1G>A), both the predicted altered splicing pattern with loss of exon 7 (AireEx7-/-) and normal full-length AIRE mRNA were found, indicating leaky rather than abolished mRNA splicing. Analysis of a corresponding mouse model demonstrated that the AireEx7-/- mutant had dramatically impaired transcriptional capacity of tissue-specific antigens in medullary thymic epithelial cells but still retained some ability to induce gene expression compared with the complete loss-of-function AireC313X-/- mutant. Our data illustrate an association between AIRE activity and the severity of autoimmune disease, with implications for more common autoimmune diseases associated with AIRE variants, such as primary adrenal insufficiency, pernicious anemia, type 1 diabetes, and rheumatoid arthritis.

[Review of clinical practice guidelines for hypoparathyroidism]

Hypoparathyroidism is a rare disorder characterized by the absent or inappropriately decreased serum parathyroid hormone in the parathyroid glands, which is accompanied by impaired calcium-phosphorus metabolism.The main etiology of hypoparathyroidism remains damage or removal of the parathyroid glands during neck surgery. In view of the incidence of thyroid cancer, primary hyperparathyroidism and other pathologies of the neck organs, which radical treatment can lead to the parathyroid gland impairment, an increased number of patients with hypoparathyroidism is expected. Autoimmune hypoparathyroidism is the second most common form of the disease, usually occurring as part of type 1 autoimmune polyglandular syndrome. Autoimmune hypoparathyroidism usually occurs in childhood and is characterized by a severe course of the disease, especially in the case of concomitant malabsorption syndrome.Chronic hypoparathyroidism of any etiology requires lifelong multicomponent therapy, as well as careful monitoring and an individual approach to choose the optimal treatment strategy. In the absence of adequate follow-up, the risks of long-term complications significantly increase, particularly in the renal, cardiovascular systems; in the soft tissues and in the brain, it could lead to visual disturbances; pathology of the musculoskeletal system with a decreased bone remodeling and a potential risk of fractures, as well as to the neurocognitive disorders and an impaired health-related quality of life.Timely diagnosis, rational medical therapy and management strategy may reduce the risks of short-term and long-term complications, frequency of hospitalizations and disability of patients, as well as improve the prognosis.This review covers the main issues of Russian guidelines for the management of chronic hypoparathyroidism, approved in 2021, including laboratory and instrumental evaluation, treatment approaches and follow-up. This guidelines also include the recommendations for special groups of patients: with acute hypocalcemia, hypoparathyroidism during pregnancy.

Characterization of the clinical and genetic spectrum of autoimmune polyendocrine syndrome type 1 in Chinese case series

BACKGROUND

Autoimmune polyendocrine syndrome type 1 (APS1) is a hereditary disease caused by mutations in the AIRE gene with both endocrine and non-endocrine organ involvement. The existing data from China are limited, and this study aims to describe the phenotypes and genetic characterization in Chinese APS1 patients. In this single-center, retrospective, observational study, comprehensive endocrine and extra-endocrine manifestations were collected, and genetic analysis in AIRE was conducted in patients with APS1 between the years of 1984 and 2018 at Peking Union Medical College Hospital.

RESULTS

In total, 13 patients from 12 unrelated families were enrolled, seven of whom were female, with hypoparathyroidism, chronic mucocutaneous candidiasis, and Addison's disease being the most frequently observed manifestations. Up to 84.7% presented with two or three of the above-mentioned manifestations, and nearly 4.9 ± 1.8 components presented in patients aged 21.2 ± 7.9 years old. Several less common phenotypes, such as myeloproliferative disease, pure red cell aplasia, renal tubular acidosis, asplenia, autoimmune hepatitis, and ankylosing spondylitis, were also observed in patients. Altogether, seven different AIRE mutations were found in six patients, four of which (K161fs, G208V, A246fs, and L308F) had not been previously reported in patients with APS1.

CONCLUSION

We have provided a comprehensive profile of Chinese patients with APS1, with less commonly observed features being observed in addition to more regularly seen manifestations. Additionally, different AIRE mutations that were observed have expanded the genetic spectrum, which will help with future understanding of the molecular pathogenesis of APS1.

Alternative splicing: Human disease and quantitative analysis from high-throughput sequencing

Alternative splicing contributes to the majority of protein diversity in higher eukaryotes by allowing one gene to generate multiple distinct protein isoforms. It adds another regulation layer of gene expression. Up to 95% of human multi-exon genes undergo alternative splicing to encode proteins with different functions. Moreover, around 15% of human hereditary diseases and cancers are associated with alternative splicing. Regulation of alternative splicing is attributed to a set of delicate machineries interacting with each other in aid of important biological processes such as cell development and differentiation. Given the importance of alternative splicing events, their accurate mapping and quantification are paramount for downstream analysis, especially for associating disease with alternative splicing. However, deriving accurate isoform expression from high-throughput RNA-seq data remains a challenging task. In this mini-review, we aim to illustrate I) mechanisms and regulation of alternative splicing, II) alternative splicing associated human disease, III) computational tools for the quantification of isoforms and alternative splicing from RNA-seq.

AAV9-mediated AIRE gene delivery clears circulating antibodies and tissue T-cell infiltration in a mouse model of autoimmune polyglandular syndrome type-1

OBJECTIVES

Autoimmune polyglandular syndrome type-1 (APS-1) is a monogenic recessive disorder characterised by multiple endocrine abnormalities, chronic mucocutaneous candidiasis and high titres of serum autoantibodies. To date, no curative treatment is available; current therapies manage the symptoms rather than treating the cause and have major side effects. APS-1 is caused by mutations in the autoimmune regulator (AIRE) gene. AIRE mediates central tolerance by directing the ectopic expression of tissue-specific antigens (TSAs) in medullary thymic epithelial cells, causing the deletion of self-reactive thymocytes. Therefore, loss-of-function mutations in AIRE result in a multisystem autoimmune disease. Because of the monogenic aetiology of APS-1 and availability of an APS-1 mouse model, we have explored the option of restoring functional AIRE using adeno-associated virus serotype 9 (AAV9).

METHODS

The efficacy of AAV9-AIRE (AAV9 carrying AIRE cDNA) gene therapy was assessed in an APS-1 mouse model. We performed intrathymic injection of AAV9-AIRE into APS-1 mouse model using ultrasound imaging technique to accurately locating the thymus. We evaluated the efficiency of this approach alongside measures of autoimmunity and histology of target tissues.

RESULTS

Intrathymic injection of AAV9-AIRE demonstrated high transduction efficiency and restored AIRE expression in the thymus. AIRE gene delivery led to a significant increase in TSA expression, and importantly a significant reduction of serum autoantibodies in treated versus control mice, which fell to near-undetectable levels by 4 weeks post-treatment. Furthermore, histological analysis of treated animals showed near-normal tissue morphology with no lymphocytic infiltrations, a hallmark of untreated Aire-deficient mice.

CONCLUSION

This study has demonstrated the feasibility of AAV9-AIRE as a vehicle for gene therapy for APS-1.

A novel variant in AIRE causing a rare, non‑classical autoimmune polyendocrine syndrome type 1

Autoimmune polyendocrine syndrome type 1 (APS‑1) is a rare inherited autoimmune disease, characterized by a classic triad, including chronic mucocutaneous candidiasis, primary adrenocortical insufficiency and hypoparathyroidism. The present study investigated phenotypes and pathogenic variants in a Chinese woman with non‑classical APS‑1. Disease‑associated variants in a patient with APS‑1 were identified via targeted next generation sequencing and the variant was confirmed via Sanger sequencing. Serum levels of calcium, phosphorus, parathyroid hormone (PTH), follicle‑stimulating hormone (FSH), luteinizing hormone (LH), estradiol and urinary levels of calcium were measured. Blood count assays and bone marrow morphology were investigated. The patient was a 32‑year‑old woman who had suffered from typical carpopedal spasms since she was 7 years old. She developed syncope, primary amenorrhea, intermittent diarrhea and general fatigue in subsequent years. Hypocalcemia, hyperphosphatemia, low levels of PTH and estradiol, elevated levels of FSH and LH, and absence of erythroblasts were observed, which indicated hypoparathyroidism, primary ovarian insufficiency and pure red cell aplasia. A novel heterozygous missense variant (NM_000383.2: c.623G>T, NP_000374.1: p.Gly208Val) in exon 5 of autoimmune regulator and a reported variant (NM_000383.2: c.371C>T, NP_000374.1: p.Pro124Leu) in exon 3 were detected, of which the c.623G>T variant may be a pathogenic variation that induces APS‑1. Under a regular follow‑up and therapeutic adjustment of calcium, calcitriol, hormone replacement therapy and methylprednisolone, the endocrine function and clinical symptoms of the patient were notably improved. The results of the present study expand the known genetic and phenotypical spectra of APS‑1.

A case report and literature review: Identification of a novel AIRE gene mutation associated with Autoimmune Polyendocrine Syndrome Type 1 in East Asians

RATIONALE

Autoimmune polyendocrine syndrome type 1 (APS-1), also referred as the autoimmune polyendocrinopathy candidiasis-ectodermal dystrophy (APECED), is a rare autosomal inherited disease predominantly among Caucasians from Northern Europe. This syndrome is very rare in East Asian population.

PATIENTS CONCERNS

Here, we describe a case of a 15-year-old Chinese boy admitted due to a 1-month history of intermittent fatigue, nausea, vomiting, and diarrhea. His symptom became worse accompanied with chest tightness 4 days before admission. On physical examination, his temperature was 38.5°C, blood pressure was 75/38 mm Hg, and pulse was 98/min. He was a thin boy with mild hyperpigmentation and xanthochromia.

DIAGNOSIS

After abdominal computed technology and laboratory tests, his diagnosis was APS-1 accompanied with adrenal crisis. Further investigation on whole-exome sequencing revealed a novel homozygous mutation c.47C>G (p.T16R) in exon 1 in the autoimmune regulator (AIRE) gene.

INTERVENTIONS

This patient underwent replacement therapy of glucocorticoids, corticosteroid, and levothyroxine, as well as calcium and calcitriol supplementation.

OUTCOMES

He continues to do well 4 years after his hospitalization. During his last follow-up, he had serum thyroid-stimulating hormone level of 3.07 μIU/mL, free triiodothyronine level of 1.92 pg/mL, and free thyroxine level of 13.95 pg/mL. His serum cortisol and ACTH (8 a.m.) levels were 28.53 μg/dL and 69.48 pg/mL, respectively.

LESSONS

APS-1 is very rare in East Asians and the variable clinical presentations of the disease make the initial diagnosis especially difficult. Autoimmune thyroiditis, type 1 diabetes mellitus, and hepatitis were the three most frequent minor components of APS-1 in East Asian patients with age of onset in late teens and 20s. Sequence analysis of AIRE gene is necessary to verify its diagnostic efficacy in association with clinical findings.

Standards of care for hypoparathyroidism in adults: a Canadian and International Consensus

PURPOSE

To provide practice recommendations for the diagnosis and management of hypoparathyroidism in adults.

METHODS

Key questions pertaining to the diagnosis and management of hypoparathyroidism were addressed following a literature review. We searched PubMed, MEDLINE, EMBASE and Cochrane databases from January 2000 to March 2018 using keywords 'hypoparathyroidism, diagnosis, treatment, calcium, PTH, calcidiol, calcitriol, hydrochlorothiazide and pregnancy'. Only English language papers involving humans were included. We excluded letters, reviews and editorials. The quality of evidence was evaluated based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. These standards of care for hypoparathyroidism have been endorsed by the Canadian Society of Endocrinology and Metabolism.

RESULTS

Hypoparathyroidism is a rare disease characterized by hypocalcemia, hyperphosphatemia and a low or inappropriately normal serum parathyroid hormone level (PTH). The majority of cases are post-surgical (75%) with nonsurgical causes accounting for the remaining 25% of cases. A careful review is required to determine the etiology of the hypoparathyroidism in individuals with nonsurgical disease. Hypoparathyroidism is associated with significant morbidity and poor quality of life. Treatment requires close monitoring as well as patient education. Conventional therapy with calcium supplements and active vitamin D analogs is effective in improving serum calcium as well as in controlling the symptoms of hypocalcemia. PTH replacement is of value in lowering the doses of calcium and active vitamin D analogs required and may be of value in lowering long-term complications of hypoparathyroidism. This manuscript addresses acute and chronic management of hypoparathyroidism in adults.

MAIN CONCLUSIONS

Hypoparathyroidism requires careful evaluation and pharmacologic intervention in order to improve serum calcium and control the symptoms of hypocalcemia. Frequent laboratory monitoring of the biochemical profile and patient education is essential to achieving optimal control of serum calcium.

Medical Hypoparathyroidism

Hypoparathyroidism is a metabolic disorder characterized by hypocalcemia, hyperphosphatemia, and inadequate levels of or function of parathyroid hormone (PTH). The authors review the nonsurgical or medical causes of hypoparathyroidism. The most common of the nonsurgical causes is autoimmune destruction of the parathyroid. Magnesium deficiency or excess can cause a functional hypoparathyroidism. Genetic conditions result in hypoparathyroidism as part of a syndrome or in isolation. Pseudohypoparathyroidism reflects a resistance to PTH. Infiltrative, metastatic, radiation destruction, mineral deposition, or idiopathic are uncommon causes of hypoparathyroidism. This article reviews the causes of hypoparathyroidism and an approach to the evaluation of this condition.

Splicing analysis of rare/novel synonymous or intronic variants identified in ABCB11 heterozygotes presenting as progressive intrahepatic cholestasis with low γ-glutamyltransferase

AIM

The aim of this study was to analyze the pathogenicity of rare/novel synonymous or intronic variants identified in ABCB11 heterozygotes presenting as progressive intrahepatic cholestasis with low γ-glutamyltransferase.

METHODS

The enrolled variants were identified in ABCB11 between October 2009 and June 2016. The effects on pre-RNA splicing were analyzed by in silico tools and minigene splicing assay.

RESULTS

There were three intronic (c.908 + 5G > A, c.2815-8A > G, and c.612-15_-6del10bp) and two synonymous (c.1809G > A, p.K603 K and c.2418C > T, p.G806G) variants with unknown significance identified in ABCB11 of five ABCB11 heterozygotes. Parental studies were carried out for four patients, and revealed that the variants with unknown significance were compound heterozygous with other pathogenic variants. The five variants with unknown significance had minor allele frequency <0.1% or were absent from controls, and had positive prediction results by in silico tools. The effects on pre-RNA splicing were further confirmed by minigene splicing assay. c.908 + 5A caused abnormal splicing in at least 78.5 ± 3.8% of products using a cryptic splice site (ss) 22 nucleotides (nt) upstream of the wild-type (WT) 5'ss. Seven nucleotides of intron 22 upstream of the WT 3'ss was retained for all products from c.2815-8G. c.612-15_-6del caused exon 8 skipping in 24.8 ± 7.7% of products, and 55 nt of exon 8 downstream of the WT 3'ss removal in remaining products. c.1809A led to exon 15 skipping. c.2418 T removed exon 20 and 62 nt of exon 21 downstream of the WT 3'ss by using a cryptic ss.

CONCLUSIONS

We successfully identified five pathogenic synonymous or intronic variants with some common features. These features might help to choose the right variant for further functional assay.

A new mutation site in the AIRE gene causes autoimmune polyendocrine syndrome type 1

Autoimmune polyendocrine syndrome type 1 (APS-1, OMIM 2403000) is a rare autosomal recessive disease that is caused by autoimmune regulator (AIRE). The main symptoms of APS-1 are chronic mucocutaneous candidiasis, autoimmune adrenocortical insufficiency (Addison's disease) and hypoparathyroidism. We collected APS-1 cases and analysed them. The AIRE genes of the patient and his family members were sequenced to identify whether the APS-1 patient had an AIRE mutation. We discovered a mutation site (c.206A>C) that had never before been reported in the AIRE gene located in exon 2 of the AIRE gene. This homogyzous mutation caused a substitution of the 69th amino acid of the AIRE protein from glutamine to proline (p.Q69P). A yeast two-hybrid assay, which was used to analyse the homodimerization properties of the mutant AIRE protein, showed that the mutant AIRE protein could not interact with the normal AIRE protein. Flow cytometry and RT-qPCR analyses indicated that the new mutation site could decrease the expression levels of the AIRE, glutamic acid decarboxylase 65 (GAD65) and tryptophan hydroxylase-1 (TPH1) proteins to affect central immune tolerance. In conclusion, our research has shown that the new mutation site (c.206A>C) may influence the homodimerization and expression levels and other aspects of the AIRE protein. It may also impact the expression levels of tissue-restricted antigens (TRAs), leading to a series of autoimmune diseases.

AIRE-mutations and autoimmune disease

The gene causing the severe organ-specific autoimmune disease autoimmune polyendocrine syndrome type-1 (APS-1) was identified in 1997 and named autoimmune regulator (AIRE). AIRE plays a key role in shaping central immunological tolerance by facilitating negative selection of T cells in the thymus, building the thymic microarchitecture, and inducing a specific subset of regulatory T cells. So far, about 100 mutations have been identified. Recent advances suggest that certain mutations located in the SAND and PHD1 domains exert a dominant negative effect on wild type AIRE resulting in milder seemingly common forms of autoimmune diseases, including pernicious anemia, vitiligo and autoimmune thyroid disease. These findings indicate that AIRE also contribute to autoimmunity in more common organ-specific autoimmune disorders.

[Clinical analysis and autoimmune regulator gene mutation of autoimmune polyendocrinopathy syndrome type I in a family: a report of one case]

The clinical data of one patient with autoimmune polyendocrinopathy syndrome type I were collected. PCR-DNA direct bidirectional sequencing was applied for mutation screening of 14 exons in autoimmune regulator (AIRE) gene in the patient and her parents. A total of 50 unrelated healthy controls were selected and tested. The bioinformatic methods were used to predict the possible impact of the mutations on the structure and function of the AIRE protein. The results of sequencing showed that heterozygous mutation c.622G>T (p.G208W) in exon 5 of the AIRE gene was detected in the patient and was a novel mutation, which had not been reported in the HGMD database and latest articles. This mutation was not detected in the 50 unrelated normal controls. The novel mutation of c.622G>T (p.G208W) in AIRE gene might play an important role in the pathogenesis of this case of autoimmune polyendocrinopathy syndrome type I.

[Clinical analysis and autoimmune regulator gene mutation of autoimmune polyendocrinopathy syndrome type I in a family: a report of one case]

The clinical data of one patient with autoimmune polyendocrinopathy syndrome type I were collected. PCR-DNA direct bidirectional sequencing was applied for mutation screening of 14 exons in autoimmune regulator (AIRE) gene in the patient and her parents. A total of 50 unrelated healthy controls were selected and tested. The bioinformatic methods were used to predict the possible impact of the mutations on the structure and function of the AIRE protein. The results of sequencing showed that heterozygous mutation c.622G>T (p.G208W) in exon 5 of the AIRE gene was detected in the patient and was a novel mutation, which had not been reported in the HGMD database and latest articles. This mutation was not detected in the 50 unrelated normal controls. The novel mutation of c.622G>T (p.G208W) in AIRE gene might play an important role in the pathogenesis of this case of autoimmune polyendocrinopathy syndrome type I.

Novel Findings into AIRE Genetics and Functioning: Clinical Implications

Autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), formerly known as autoimmune polyendocrine syndrome type 1, is a paradigm of a monogenic autoimmune disease caused by mutations of a gene, named autoimmune regulator (AIRE). AIRE acts as a transcription regulator that promotes immunological central tolerance by inducing the ectopic thymic expression of many tissue-specific antigens. Although the syndrome is a monogenic disease, it is characterized by a wide variability of the clinical expression with no significant correlation between genotype and phenotype. Indeed, many aspects regarding the exact role of AIRE and APECED pathogenesis still remain unraveled. In the last decades, several studies in APECED and in its mouse experimental counterpart have revealed new insights on how immune system learns self-tolerance. Moreover, novel interesting findings have extended our understanding of AIRE's function and regulation thus improving our knowledge on the pathogenesis of APECED. In this review, we will summarize recent novelties on molecular mechanisms underlying the development of APECED and their clinical implications.

Identification of novel PKD1 and PKD2 mutations in a Chinese population with autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequently inherited renal diseases caused by mutations in PKD1 and PKD2. We performed mutational analyses of PKD genes in 49 unrelated patients using direct PCR-sequencing and multiplex ligation-dependent probe amplification (MLPA) for PKD1 and PKD2. RT-PCR analysis was also performed in a family with a novel PKD2 splicing mutation. Disease-causing mutations were identified in 44 (89.8%) of the patients: 42 (95.5%) of the patients showed mutations in PKD1, and 2 (4.5%) showed mutations in PKD2. Ten nonsense, 17 frameshift, 4 splicing and one in-frame mutation were found in 32 of the patients. Large rearrangements were found in 3 patients, and missense mutations were found in 9 patients. Approximately 61.4% (27/44) of the mutations are first reported with a known mutation rate of 38.6%. RNA analysis of a novel PKD2 mutation (c.595_595 + 14delGGTAAGAGCGCGCGA) suggested monoallelic expression of the wild-type allele. Furthermore, patients with PKD1-truncating mutations reached end-stage renal disease (ESRD) earlier than patients with non-truncating mutations (47 ± 3.522 years vs. 59 ± 11.687 years, P = 0.016). The mutation screening of PKD genes in Chinese ADPKD patients will enrich our mutation database and significantly contribute to improve genetic counselling for ADPKD patients.

Cohen's h for detection of disease association with rare genetic variants

BACKGROUND

The power of the genome wide association studies starts to go down when the minor allele frequency (MAF) is below 0.05. Here, we proposed the use of Cohen's h in detecting disease associated rare variants. The variance stabilizing effect based on the arcsine square root transformation of MAFs to generate Cohen's h contributed to the statistical power for rare variants analysis. We re-analyzed published datasets, one microarray and one sequencing based, and used simulation to compare the performance of Cohen's h with the risk difference (RD) and odds ratio (OR).

RESULTS

The analysis showed that the type 1 error rate of Cohen's h was as expected and Cohen's h and RD were both less biased and had higher power than OR. The advantage of Cohen's h was more obvious when MAF was less than 0.01.

CONCLUSIONS

Cohen's h can increase the power to find genetic association of rare variants and diseases, especially when MAF is less than 0.01.

A novel mutation in autoimmune regulator gene causes autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy

BACKGROUND

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome (APECED) is a rare autosomal recessive disease due to mutations in the autoimmune regulator (AIRE) gene, which encodes a transcription factor that induces the expression of peripheral tissue-specific antigens in medullary thymic epithelial cells.

AIM

The purpose of this study was to identify the underlying genetic cause in a Chinese family diagnosed with APECED.

METHOD

Peripheral blood samples were collected from family members. All exons of the AIRE gene and adjacent exon-intron sequences were amplified by PCR and subsequently sequenced. The functional consequence of the mutations was analyzed by cell transfection and in vitro assays.

RESULTS

A novel c.483_484insC mutation in exon 4 was identified, which resulted in a frame shift predicted to generate a truncated protein containing the first 163 AIRE amino acids followed by 52 aberrant amino acids. Confocal immunofluorescence microscopy of COS-7 cells transfected with wild-type and mutant AIRE constructs showed that wild-type AIRE protein was localized mainly in the nucleus, while mutant AIRE was localized mainly in the cytoplasm. A luciferase reporter assay showed that the identified mutation dramatically inhibited the transactivation activity of AIRE in vitro.

CONCLUSION

We identified a novel AIRE mutation which alters the intracellular location and transcription activity of AIRE, and has implications in the pathogenesis of APECED.

Biomarkers of mercury exposure in the Amazon

Mercury exposure in the Amazon has been studied since the 1980s decade and the assessment of human mercury exposure in the Amazon is difficult given that the natural occurrence of this metal is high and the concentration of mercury in biological samples of this population exceeds the standardized value of normality established by WHO. Few studies have focused on the discovery of mercury biomarkers in the region's population. In this way, some studies have used genetics as well as immunological and cytogenetic tools in order to find a molecular biomarker for assessing the toxicological effect of mercury in the Amazonian population. Most of those studies focused attention on the relation between mercury exposure and autoimmunity and, because of that, they will be discussed in more detail. Here we introduce the general aspects involved with each biomarker that was studied in the region in order to contextualize the reader and add information about the Amazonian life style and health that may be considered for future studies. We hope that, in the future, the toxicological studies in this field use high technological tools, such as the next generation sequencing and proteomics skills, in order to comprehend basic questions regarding the metabolic route of mercury in populations that are under constant exposure, such as in the Amazon.