Protein-altering variants of PTPN2 in childhood-onset Type 1A diabetes

AIM

To examine the contribution of PTPN2 coding variants to the risk of childhood-onset Type 1A diabetes.

METHODS

PTPN2 mutation analysis was carried out for 169 unrelated Japanese people with childhood-onset Type 1A diabetes. We searched for coding variants that were absent or extremely rare in the general population and were scored as damaging by multiple in silico programs. We performed mRNA analysis and three-dimensional structural prediction of the detected variants, when possible. We also examined possible physical links between these variants and previously reported risk SNPs as well as clinical information from variant-positive children.

RESULTS

One frameshift variant (p.Q286Yfs*24) and two probably damaging missense substitutions (p.C232W and p.R350Q) were identified in one child each. Of these, p.Q286Yfs*24 and p.C232W were hitherto unreported, while p.R350Q accounted for 2/121,122 alleles of the exome datasets. The p.Q286Yfs*24 variant did not encode stable mRNA, and p.C232W appeared to affect the structure of the tyrosine-protein phosphatase domain. The three variants were physically unrelated to known risk SNPs. The variant-positive children manifested Type 1A diabetes without additional clinical features and invariably carried risk human leukocyte antigen alleles.

CONCLUSIONS

The results provide the first indication that PTPN2 variants contribute to the risk of Type 1A diabetes, independently of known risk SNPs. PTPN2 coding variants possibly induce non-specific Type 1A diabetes phenotypes in individuals with human leukocyte antigen-mediated disease susceptibility. Our findings warrant further validation.

Abstract P6-12-26: The axonal damage marker, serum phosphorylated neurofilament heavy subunit, as a potential marker of chemotherapy-induced neuropathy

Background: Chemotherapy-induced neurologic disorders such as peripheral neuropathy and cognitive disturbance are clinically significant problems for cancer survivors, but their objective assessment methods have not been established. We previously reported in a cross-sectional study that the serum phosphorylated neurofilament heavy subunit (pNF-H), a biomarker of axonal damage, was increased in breast cancer patients treated with chemotherapy. The aim of this study is to temporally assess the neurological adverse events and evaluate the association of serum pNF-H level with cognitive functions and neuropathy following sequential chemotherapy.

Methods: Thirty-five breast cancer patients who received neoadjuvant or adjuvant chemotherapy were enrolled prospectively. They underwent brain MRI and cognitive function tests including Controlled Oral Word Association (COWA), Trail Making Test (TMT), and Hopkins Verbal Learning Test-Revised (HVLT-R) before chemotherapy (baseline), one month after completing sequential chemotherapy (post-phase) and more than six months after completing chemotherapy (late-phase). Serum pNF-H levels and questionnaires reporting peripheral neuropathy were measured at the three phases, and every 3 weeks during chemotherapy. Brain MRI volumetry was calculated by the automatic analysis software, BAAD® (Brain Anatomical Analysis using Dartel). The correlations among cognitive functions, brain volume, peripheral neuropathy and serum pNF-H levels were statistically analyzed.

Results: Patients' median age was 48 years (range 24-71). A decrease of more than 10% in cognitive function test (COWA) scores was seen in 10 cases (31%) at post-phase. A brain volume loss of more than 10% was seen in 5 cases (15%) at post-phase. The correlation between brain volume change and cognitive disturbance was not significant (p=0.45) and both changes were improved at late-phase. A peripheral neuropathy grade above CTCAE grade 2 was seen in 19 cases (54%). The neuropathy was significantly more severe in anthracycline followed by taxane regimen than taxane followed by anthracycline during chemotherapy (p=0.016), although this difference was not seen at the late-phase (p=0.08). An elevated serum pNF-H level at baseline was seen in only one case, and this case demonstrated the cognitive disturbance, brain volume loss, and peripheral neuropathy following chemotherapy. During chemotherapy, pNF-H was elevated in 24 patients (69%), with especially higher levels noted during the taxane regimen compared to the anthracycline regimen (p=0.019). In the cases treated with anthracycline followed by taxane, the taxane-phase elevation was especially significant (p=0.014). The maximum pNF-H level during taxane therapy was significantly correlated with peripheral neuropathy grade (p=0.002). At late-phase, the significant reduction of pNF-H level was seen in all cases.

Conclusions: Change of cognitive function, brain volume and peripheral neuropathy was observed following chemotherapy in breast cancer patients. This study suggests that the serum axonal damage marker, pNF-H, may reflect chemotherapy-induced neuropathy.

Citation Format: Kida K, Sumitani M, Ogata T, Kotake R, Natori A, Hashimoto J, Shimokawa T, Yamauchi H, Yamauchi T. The axonal damage marker, serum phosphorylated neurofilament heavy subunit, as a potential marker of chemotherapy-induced neuropathy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-26.

Next-generation sequencing for patients with non-obstructive azoospermia: implications for significant roles of monogenic/oligogenic mutations

Azoospermia affects up to 1% of adult men. Non-obstructive azoospermia is a multifactorial disorder whose molecular basis remains largely unknown. To date, mutations in several genes and multiple submicroscopic copy-number variations (CNVs) have been identified in patients with non-obstructive azoospermia. The aim of this study was to clarify the contribution of nucleotide substitutions in known causative genes and submicroscopic CNVs in the genome to the development of non-obstructive azoospermia. To this end, we conducted sequence analysis of 25 known disease-associated genes using next-generation sequencing and genome-wide copy-number analysis using array-based comparative genomic hybridization. We studied 40 Japanese patients with idiopathic non-obstructive azoospermia. Functional significance of molecular alterations was assessed by in silico analyses. As a result, we identified four putative pathogenic mutations, four rare polymorphisms possibly associated with disease risk, and four probable neutral variants in 10 patients. These sequence alterations included a heterozygous splice site mutation in SOHLH1 and a hemizygous missense substitution in TEX11, which have been reported as causes of non-obstructive azoospermia. Copy-number analysis detected five X chromosomal or autosomal CNVs of unknown clinical significance, in addition to one known pathogenic Y chromosomal microduplication. Five patients carried multiple molecular alterations. The results indicate that monogenic and oligogenic mutations, including those in SOHLH1 and TEX11, account for more than 10% of cases of idiopathic non-obstructive azoospermia. Furthermore, this study suggests possible contributions of substitutions in various genes as well as submicroscopic CNVs on the X chromosome and autosomes to non-obstructive azoospermia, which require further validation.

Overexpression of an Arabidopsis thaliana galactinol synthase gene improves drought tolerance in transgenic rice and increased grain yield in the field

Drought stress has often caused significant decreases in crop production which could be associated with global warming. Enhancing drought tolerance without a grain yield penalty has been a great challenge in crop improvement. Here, we report the Arabidopsis thaliana galactinol synthase 2 gene (AtGolS2) was able to confer drought tolerance and increase grain yield in two different rice (Oryza sativa) genotypes under dry field conditions. The developed transgenic lines expressing AtGolS2 under the control of the constitutive maize ubiquitin promoter (Ubi:AtGolS2) also had higher levels of galactinol than the non-transgenic control. The increased grain yield of the transgenic rice under drought conditions was related to a higher number of panicles, grain fertility and biomass. Extensive confined field trials using Ubi:AtGolS2 transgenic lines in Curinga, tropical japonica and NERICA4, interspecific hybrid across two different seasons and environments revealed the verified lines have the proven field drought tolerance of the Ubi:AtGolS2 transgenic rice. The amended drought tolerance was associated with higher relative water content of leaves, higher photosynthesis activity, lesser reduction in plant growth and faster recovering ability. Collectively, our results provide strong evidence that AtGolS2 is a useful biotechnological tool to reduce grain yield losses in rice beyond genetic differences under field drought stress.