Disruptive NADSYN1 Variants Implicated in Congenital Vertebral Malformations

Supplementation with NAD+ and its precursors: A rescue of female reproductive diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme involved in many pathophysiological processes. Supplementation with NAD+ and its precursors has been demonstrated as an emerging therapeutic strategy for the diseases. NAD+ also plays an important role in the reproductive system. Here, we summarize the function of NAD+ in various reproductive diseases and review the application of NAD+ and its precursors in the preservation of reproductive capacity and the prevention of embryonic malformations. It is shown that NAD+ shows good promise as a therapeutic approach for saving reproductive capacity.

Inhibitors of NAD+ Production in Cancer Treatment: State of the Art and Perspectives

The addiction of tumors to elevated nicotinamide adenine dinucleotide (NAD+) levels is a hallmark of cancer metabolism. Obstructing NAD+ biosynthesis in tumors is a new and promising antineoplastic strategy. Inhibitors developed against nicotinamide phosphoribosyltransferase (NAMPT), the main enzyme in NAD+ production from nicotinamide, elicited robust anticancer activity in preclinical models but not in patients, implying that other NAD+-biosynthetic pathways are also active in tumors and provide sufficient NAD+ amounts despite NAMPT obstruction. Recent studies show that NAD+ biosynthesis through the so-called "Preiss-Handler (PH) pathway", which utilizes nicotinate as a precursor, actively operates in many tumors and accounts for tumor resistance to NAMPT inhibitors. The PH pathway consists of three sequential enzymatic steps that are catalyzed by nicotinate phosphoribosyltransferase (NAPRT), nicotinamide mononucleotide adenylyltransferases (NMNATs), and NAD+ synthetase (NADSYN1). Here, we focus on these enzymes as emerging targets in cancer drug discovery, summarizing their reported inhibitors and describing their current or potential exploitation as anticancer agents. Finally, we also focus on additional NAD+-producing enzymes acting in alternative NAD+-producing routes that could also be relevant in tumors and thus become viable targets for drug discovery.

Molecular landscape of congenital vertebral malformations: recent discoveries and future directions

Vertebral malformations (VMs) pose a significant global health problem, causing chronic pain and disability. Vertebral defects occur as isolated conditions or within the spectrum of various congenital disorders, such as Klippel-Feil syndrome, congenital scoliosis, spondylocostal dysostosis, sacral agenesis, and neural tube defects. Although both genetic abnormalities and environmental factors can contribute to abnormal vertebral development, our knowledge on molecular mechanisms of numerous VMs is still limited. Furthermore, there is a lack of resource that consolidates the current knowledge in this field. In this pioneering review, we provide a comprehensive analysis of the latest research on the molecular basis of VMs and the association of the VMs-related causative genes with bone developmental signaling pathways. Our study identifies 118 genes linked to VMs, with 98 genes involved in biological pathways crucial for the formation of the vertebral column. Overall, the review summarizes the current knowledge on VM genetics, and provides new insights into potential involvement of biological pathways in VM pathogenesis. We also present an overview of available data regarding the role of epigenetic and environmental factors in VMs. We identify areas where knowledge is lacking, such as precise molecular mechanisms in which specific genes contribute to the development of VMs. Finally, we propose future research avenues that could address knowledge gaps.

Metabolic Alterations in NADSYN1-Deficient Cells

NAD synthetase 1 (encoded by the gene NADSYN1) is a cytosolic enzyme that catalyzes the final step in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) from tryptophan and nicotinic acid. NADSYN1 deficiency has recently been added to the spectrum of congenital NAD+ deficiency disorders. To gain insight into the metabolic consequences of NADSYN1 deficiency, the encoding gene was disrupted in A549 and HEK293T cells, and the metabolome was profiled in the presence of different NAD+ precursors, including tryptophan, nicotinamide and nicotinic acid. We demonstrate that when precursors of the NAD+ salvage pathway in the form of nicotinamide become limiting, NADSYN1 deficiency results in a decline in intracellular NAD+ levels even in the presence of other potential NAD+ sources such as tryptophan and nicotinic acid. As a consequence, alterations in 122 and 69 metabolites are observed in NADSYN1-deficient A549 and HEK293T cells compared to the wild-type cell line (FC > 2 and p < 0.05). We thus show that NADSYN1 deficiency results in a metabolic phenotype characterized by alterations in glycolysis, the TCA cycle, the pentose phosphate pathway, and the polyol pathway.

Nicotinamide Adenine Dinucleotide Deficiency and Its Impact on Mammalian Development

Significance: Nicotinamide adenine dinucleotide (NAD) is an important molecule synthesized from tryptophan or vitamin B3 and involved in numerous cellular reactions. NAD deficiency during pregnancy causes congenital NAD deficiency disorder (CNDD) characterized by multiple congenital malformations and/or miscarriage. Studies in genetically engineered mice replicating mutations found in human patient cases show that CNDD can be prevented by dietary supplements. Recent Advances: A growing number of patient reports show that biallelic loss-of-function of genes involved in NAD de novo synthesis (KYNU, HAAO, NADSYN1) cause CNDD. Other factors that limit the availability of NAD precursors, for example, limited dietary precursor supply or absorption, can cause or contribute to NAD deficiency and result in CNDD in mice. Molecular flux experiments allow quantitative understanding of NAD precursor concentrations in the circulation and their usage by different cells. Studies of NAD-consuming enzymes and contributors to NAD homeostasis help better understand how perturbed NAD levels are implicated in various diseases and adverse pregnancy outcomes. Critical Issues: NAD deficiency is one of the many known causes of adverse pregnancy outcomes, but its prevalence in the human population and among pregnant women is unknown. Since NAD is involved in hundreds of diverse cellular reactions, determining how NAD deficiency disrupts embryogenesis is an important challenge. Future Directions: Furthering our understanding of the molecular fluxes between the maternal and embryonic circulation during pregnancy, the NAD-dependent pathways active in the developing embryo, and the molecular mechanisms by which NAD deficiency causes adverse pregnancy outcomes will provide direction for future prevention strategies. Antioxid. Redox Signal. 39, 1108-1132.

Adult patient diagnosed with NADSYN1 associated congenital NAD deficiency and analysis of NAD levels to be published in: European Journal of Medical Genetics

INTRODUCTION

Nicotinamide adenine dinucleotide (NAD) is an essential cosubstrate/coenzyme in multiple cellular redox processes and a substrate in several non-redox reactions. NADSYN1 encodes NAD synthetase 1, an enzyme in the NAD de novo synthesis pathway and the Preiss-Handler pathway, and biallelic pathogenic variants causes NAD deficiency associated with vertebral, cardiac, renal and limb defects. Szot et al. and Kortbawi et al. have reported a total of seven patients with NADSYN1 associated congenital NAD deficiency disorder with the oldest patient being seven years old.

PATIENT DATA

We present a male patient age 30 with a height of 130 cm and numerous skeletal malformations including segmentation defects of the spine, rib anomalies and unequal leg length as well as bilateral ptosis, cleft palate and asymmetric dysmorphic facial features. The patient underwent surgery for an aortic stenosis due to a bicuspid valve. No malformations of the kidneys or urinary tract were identified.

RESULTS

Trio exome sequencing revealed a homozygous missense variant in NADSYN1 c.1717G > A (p.Ala573Thr). Both parents were unaffected carriers of the variant. Analysis of NAD levels showed that the patient had a lower NAD pool compared to his unaffected siblings. The NAD pool rose approximately 25% after supplementation with nicotinamide, a NAD precursor for the salvage pathway.

CONCLUSION

The variant was previously reported in four patients and functional analyses by Szot et al. support the pathogenicity of the variant. We report an adult patient with NADSYN1 associated congenital NAD deficiency disorder and expand the phenotypic spectrum. We also present analysis of the NAD levels before and after supplementation with nicotinamide.

Integrating RNA-seq and scRNA-seq to explore the biological significance of NAD + metabolism-related genes in the initial diagnosis and relapse of childhood B-cell acute lymphoblastic leukemia

BACKGROUND

Nicotinamide Adenine Dinucleotide (NAD) depletion is reported to be a potential treatment for B-cell Acute Lymphoblastic Leukemia (B-ALL), but the mechanism of NAD metabolism-related genes (NMRGs) in B-ALL relapse remains unclear.

METHODS

Transcriptome data (GSE3912), and single-cell sequencing data (GSE130116) of B-ALL patients were downloaded from Gene Expression Omnibus (GEO) database. NMRGs were sourced from Kyoto Encyclopedia of Genes and Genomes (KEGG) and Reactome databases. Further, the differentially expressed NMRGs (DE-NMRGs) were selected from the analysis between initial diagnosis and relapse B-ALL samples, which further performed functional enrichment analyses. The biomarkers were obtained through random forest (RF) algorithm and repeated cross validation. Additionally, cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT) algorithm was used to evaluate the immune cell differences between the initial diagnosis and relapse samples, and the correlations between biomarkers and gene markers of differential immune cells were analyzed. Furthermore, single cell RNA sequencing was conducted in the GSE130116 dataset to find key cell clusters. In addition, according to biomarkers expressions, cell clusters were categorized into high and low biomarker expression groups, and Gene Set Enrichment Analysis (GSEA) analysis was performed on them. Finally, the cell clusters with the highest expression of biomarkers were selected to explore the roles of biomarkers in different cell clusters and identify transcription factors (TFs) influencing biological markers.

RESULTS

23 DE-NMRGs were screened out, which were mainly enriched in nucleoside phosphate metabolic process, nucleotide metabolic process, and Nicotinate and nicotinamide metabolism. Moreover, 3 biomarkers (NADSYN1, SIRT3, and PARP6) were identified from the machine learning. CIBERSORT results demonstrated that four types of immune cells (B Cells naive, Monocyte, Neutrophils, and T cells CD4 memory Activated) were significantly different between the initial diagnosis and the relapse B-ALL samples, and there were strong correlations between biomarkers and differential immune cells such as positive correlation between NADSYN1 and B Cells naive. The single cell analyses showed that the biomarkers were highly expressed in common myeloid progenitors (CMP), granulocyte-macrophage progenitor (GMP), and megakaryocyte-erythroid progenitor (MEP) cell clusters. Gene set enrichment analysis (GSEA) results indicated that 55 GO terms and 3 KEGG pathways were enriched by the genes in high and low biomarker expression groups. It was found that TF CREB3L2(+) was significantly reduced in the high expression group, which may be the TF affecting biomarkers in the high expression group.

CONCLUSION

This study identified NADSYN1, SIRT3, and PARP6 as the biomarkers of B-ALL, explored biological significance of NMRGs in the initial diagnosis and relapse of B-ALL, and revealed mechanism of biomarkers at the level of the single cell.