Rapid Genetic Diagnosis of Citrin Deficiency by Multicolor Melting Curve Analysis

Clinical and genetic analysis of 26 Chinese patients with neonatal intrahepatic cholestasis due to citrin deficiency

BACKGROUND

Neonatal intrahepatic cholestasis due to citrin deficiency (NICCD) is an autosomal recessive disorder caused by SLC25A13 genetic mutations. We retrospectively analyzed 26 Chinese infants with NICCD (years 2014-2022) in Quanzhou City.

METHODS

The plasma citrulline (CIT) concentration analyzed by tandem mass spectrometry (MS/MS), biochemical parameters and molecular analysis results are presented.

RESULTS

Twelve genotypes were discovered. The relationship between the CIT concentration and genotype is uncertain. In total, 8 mutations were detected, with 4 variations, c.851_854delGTAT, c.615 + 5G > A, c.1638_1660dup and IVS16ins3kb, constituting the high-frequency mutations. Specifically, we demonstrated 2 patients with NICCD combined with another inborn errors of metabolism (IEM). Patient No. 22 possessed compound heterozygous mutations of c.615 + 5G > A and c.790G > A in the SLC25A13 gene accompanied by compound heterozygous variations of c.C259T and c.A155G in the PTS gene. Additionally, Patient No. 26 carried c.51C > G and c.760C > T in the SLC22A5 gene as well as c.615 + 5G > A and IVS16ins3kb in the SLC25A13 gene.

CONCLUSIONS

We report a case of the simultaneous occurrence of primary carnitine deficiency (PCD) and NICCD.

One-step genotyping of α-thalassaemia by multiplex symmetric PCR melting curve

AIMS

Alpha-thalassaemia is one of the most common monogenic disorders worldwide. Due to high guanine-cytosine (GC) content and high mutation diversity in α-globin gene cluster, deletional and non-deletional mutations were usually separately detected with different methods. The aim of this study was to develop a novel one-step method for α-thalassaemia genotyping.

METHODS

A multiplex symmetric PCR melting curve strategy was designed for one-step α-thalassaemia genotyping. Based on this strategy, a novel method was developed to simultaneously detect four common deletional (-α3.7 , -α4.2 , _ _SEA , --THAI ) and five common non-deletional (αCD30(-GAG)α, αCD31(G>A)α, αWSα, αQSα, αCSα) α-thalassaemia mutations in a closed-tube reaction. This method was also evaluated by double-blind detection of 235 genotype-known samples and 1630 clinical samples.

RESULTS

All nine α-thalassaemia mutations could be accurately identified by this novel method within 3 hours. The evaluation results also showed a 100% concordance with comparison methods.

CONCLUSIONS

This method is rapid, accurate, low-cost and easy to operate, which can be used for molecular screening and genetic diagnosis of α-thalassaemia in clinical practice. The multiplex symmetric PCR melting curve strategy designed in this study can also provide an effective approach to the method development for high GC content templates and multiple mutations.

Citrin Deficiency: Clinical and Nutritional Features

SLC25A13 gene mutations are responsible for diseases related to citrin deficiency (CD), such as neonatal intrahepatic cholestasis caused by citrin deficiency and adult-onset type II citrullinemia (CTLN2). From childhood to adulthood, CD patients are apparently healthy due to metabolic compensation with peculiar dietary habits-disliking high-carbohydrate foods and liking fat and protein-rich foods. Carbohydrate overload and alcohol consumption may trigger the sudden onset of CTLN2, inducing hyperammonemia and consciousness disturbance. Well-compensated asymptomatic CD patients are sometimes diagnosed as having non-obese (lean) non-alcoholic fatty liver disease and steatohepatitis, which have the risk of developing into liver cirrhosis and hepatocellular carcinoma. CD-induced fatty liver demonstrates significant suppression of peroxisome proliferator-activated receptor α and its downstream enzymes/proteins involved in fatty acid transport and oxidation and triglyceride secretion as a very low-density lipoprotein. Nutritional therapy is an essential and important treatment of CD, and medium-chain triglycerides oil and sodium pyruvate are useful for preventing hyperammonemia. We need to avoid the use of glycerol for treating brain edema by hyperammonemia. This review summarizes the clinical and nutritional features of CD-associated fatty liver disease and promising nutritional interventions.

The mutation spectrum of SLC25A13 gene in citrin deficiency: identification of novel mutations in Vietnamese pediatric cohort with neonatal intrahepatic cholestasis

BACKGROUND

Citrin deficiency (CD), a disorder caused by mutations in the SLC25A13 gene, may result in neonatal intrahepatic cholestasis. This study was purposely to explore the mutation spectrum of SLC25A13 gene in Vietnamese CD patients.

METHODS

The 292 unrelated CD patients were first screened for four high-frequency mutations by PCR/PCR-RFLP. Then, Sanger sequencing was performed directly for heterozygous or undetected patients. Novel mutations identified would need to be confirmed by their parents.

RESULTS

12 pathogenic SLC25A13 mutations were identified in all probands, including three deletions c.851_854del (p.R284Rfs*3), c.70-63_133del (p.Y24_72Ifs*10), and c.[1956C>A;1962del] (p.[N652K;F654Lfs*45]), two splice-site mutations (IVS6+5G>A and IVS11+1G>A), one nonsense mutations c.1399C>T (p.R467*), one duplication mutation c.1638_1660dup (p.A554fs*570), one insertion IVSl6ins3kb (p.A584fs*585), and four missense mutation c.2T>C (p.M1T), c.1231G>A (p.V411M), c.1763G>A (p.R588Q), and c.135G>C (p.L45F). Among them, c.851_854del (mut I) was the most identified mutant allele (91.78%) with a total of 247 homozygous and 42 heterozygous genotypes of carriers. Interestingly, two novel mutations were identified: c.70-63_133del (p.Y24_72Ifs*10) and c.[1956C>A;1962del] (p.[N652K;F654Lfs*45]).

CONCLUSION

The SLC25A13 mutation spectrum related to intrahepatic cholestasis infants in Vietnam revealed a quite similar pattern to Asian countries' reports. This finding supports the use of targeted SLC25A13 mutation for CD screening in Vietnam and contributed to the SLC25A13 mutation spectra worldwide. It also helps emphasize the role of DNA analysis in treatment, genetic counseling, and prenatal diagnosis.

Rare liver diseases are not rare in China

Rare diseases, also known as orphan diseases, are a group of diseases that affect a relatively small number of people. Low incidence rates, atypical symptoms, imperfect diagnosis criteria and few treatment options impose medical, psychological and financial stress on the local healthcare system. The spectrum of liver diseases in China has changed in the past decades due to successful control of once highly prevalent viral hepatitis B and C. Furthermore, the increased awareness and improved availability of specific laboratory tests have also facilitated the diagnosis of rare diseases such as autoimmune, cholestatic and genetic liver diseases. Finally, considering the huge population, the total number of many rare liver diseases in China is not as rare as once deemed. In this mini-review article, we will outline the current clinical and epidemiological profiles of some rare liver diseases that are no longer rare in China.

Obstacles to home-based dietary management for caregivers of children with citrin deficiency: a qualitative study

Background

Dietary management is the most important and effective treatment for citrin deficiency, as well as a decisive factor in the clinical outcome of patients. However, the dietary management ability of caregivers of children with citrin deficiency is generally poor, especially in East Asia where carbohydrate-based diets are predominant. The aim of this study was to identify the difficulties that caregivers encounter in the process of home-based dietary management, and the reasons responsible for these challenges.

Results

A total of 26 caregivers of children with citrin deficiency were recruited, including 24 mothers, one father, and one grandmother. Grounded theory was employed to identify three themes (covering 12 sub-themes) related to the dilemma of dietary management: dietary management that is difficult to implement; conflicts with traditional concepts; and the notion that children are only a part of family life. The first theme describes the objective difficulties that caregivers encounter in the process of dietary management; the second theme describes the underlying reasons responsible for the non-adherent behavior of caregivers; the third theme further reveals the self-compromise by caregivers in the face of multiple difficulties.

Conclusions

This study reflects the adverse effects of multi-dimensional contradictions on the adherence of caregivers to dietary management. These findings reveal that the dietary management of citrin deficiency is not only a rational process, rather it is deeply embedded in family, social, and dietary traditions.