Progress in Biological Functions of NBAS Gene and Related Diseases / 罕见病研究

Neuroblastoma-amplified sequence (NBAS) is a highly conserved gene firstly found in neuroblastoma, targeting on the human chromosome 2 p24.3 and encodes a protein that is a subunit of the Syntaxin 18 complex. The functions of NBAS include the involvement in transport of Golgi-to-Endoplasmic Reticulum retrograde and degradation of nonsense-mediated mRNA. NBAS gene is widely expressed in more than 30 tissues, suggesting that it may play an important role in human body. In 2010 and 2015, NBAS was identified successively as the pathogenic gene of SOPH syndrome and fever-related liver failure respectively. Recent studies shows that NBAS gene mutations can involve immune system and cause immune deficiency. In this paper, we review the biological function of NBAS, NBAS gene mutation-related diseases and their pathogenesis in recent years.

A 34-year-old Japanese patient exhibiting NBAS deficiency with a novel mutation and extended phenotypic variation.

Biallelic neuroblastoma amplified sequence (NBAS) gene mutations have recently been identified to cause a reduction in its protein expression and a broad phenotypic spectrum, from isolated short stature, optic nerve atrophy, and Pelger-Huët anomaly (SOPH) syndrome or infantile liver failure syndrome 2 to a combined, multi-systemic disease including skeletal dysplasia and immunological and neurological abnormalities. Herein, we report a 34-year-old patient with a range of phenotypes for NBAS deficiency due to compound heterozygous variants; one is a SOPH-specific variant, p.Arg1914His, and the other is a novel splice site variant, c.6433-2A>G. The patient experienced recurrent acute liver failure until early childhood. Hypogammaglobulinemia, a decrease in natural killer cells, and optic nerve atrophy were evident from infancy to childhood. In adulthood, the patient exhibited novel phenotypic features such as hepatic cirrhosis complicated by portal hypertension and autoimmune hemolytic anemia. The patient also suffered from childhood-onset insulin-requiring diabetes with progressive beta cell dysfunction. The patient had severe short stature and exhibited dysmorphic features compatible with SOPH, intellectual disability, and epilepsy. NBAS protein expression in the patient's fibroblasts was severely low. RNA expression analysis for the c.6433-2A>G variant showed that this variant activated two cryptic splice sites in intron 49 and exon 50, for which the predicted consequences at the protein level were an in-frame deletion/insertion, p.(Ile2199_Asn2202delins16), and a premature termination codon, p.(Ile2199Tyrfs*17), respectively. These findings indicate that NBAS deficiency is a multi-systemic progressive disease. The results of this study extend the spectrum of clinical and genetic findings related to NBAS deficiency.

Hutchinson-Gilford progeria syndrome in two brothers and literature review / 临床儿科杂志

Objective To analysis the clinical features, diagnosis and treatment of Hutchinson-Gilford progeria syndrome (HGPS). Methods The clinical data and gene testing results of HGPS in two brothers in the same family were retrospectively analyzed. The related literatures were reviewed. Results The proband was 15 years old, and his younger brother was 6 years old. Both of them presented premature appearance at 4 years old and 1 year-old respectively. Both of them suffered from underweight, short stature, reduced subcutaneous fat, bird face (prominent eyes, facial skin, scalp veins exposure, hook and prominent nose, mandibular stenosis). In addition, their trunk and limbs skin was relaxation, and they had ankylosis,and shrill voice etc.In both of them,the compound heterozygous mutation of NBAS gene(c.4081C>T,c.5741C>T)were found by full sequence exon sequencing, which were inherited from their father and mother respectively. The literature review suggested that NBAS gene mutation was associated with the diseases with main phenotype of short stature and optic atrophy.Conclusions It is reported two cases of HGPS caused by NBAS gene mutation.It is rare that two brothers have HGPS.