Clinical, Molecular and Functional Investigation on an Infant with Neonatal Intrahepatic Cholestasis Caused by Citrin Deficiency (NICCD)

BACKGROUND AND OBJECTIVE: SLC25A13 analysis has provided reliable evidences for the definitive diagnosis of citrin deficiency (CD) in the past decade. Meanwhile, these studies generated some issues yet to be resolved, including the pathogenicity of SLC25A13 missense mutations and the mRNA product from the mutation c.615+5G>A. This study aims to investigate the effect of a novel missense mutation on the aspartate/glutamate carrier (AGC) function of citrin protein, and to explore the aberrant transcript from c.615+5G>A in the same CD infant. METHODS AND RESULTS: By means of screening for prevalent SLC25A13 mutations and exons sequencing, the patient proved a compound heterozygote of c.615+5G>A and a novel c.1064G>A (p.Arg355Gln) mutation. An aberrant transcript with retention of the entire intron 6, r.[615+1_615+1789ins; 615+5 g>a] (GenBank accession number KJ128074), which was resulted from c.615+5G>A, was detected by RT-PCR and cDNA sequencing. After bioinformatic analyses of the novel missense mutation c.1064G>A, the growth abilities of three agc1Δ yeast strains were tested, which had been transformed with recombinant or empty vectors, respectively. Besides the bioinformatically pathogenic evidences, the growth ability of the agc1Δ strains transformed with mutant recombinant was the same as with empty vector, but significantly lower than that with normal control in functional analysis. CONCLUSIONS: A CD infant was definitely diagnosed in this paper by a genetic, transcriptional and functional analysis of SLC25A13 gene. This study provided direct laboratory evidences supporting the splice-site nature of the c.615+5G>A mutation, and the novel c.1064G>A variation, which proved a pathogenic mutation bioinformatically and functionally, enriched the SLC25A13 mutation spectrum.