Climate change: approach to intervention using expression vector for carbonic anhydrase via glycosylphosphatidylinositol.

Climate change is a change in the usual weather found in a place. The climate change has a major impact not only on natural disasters of the Earth but also on human health. The climate crisis is then no longer a future concern. It includes both the global warming driven by human emissions of greenhouse gases (GHG), and the resulting large-scale shifts in weather patterns. Global warming can occur from a variety of causes, both natural and human induced. The primary GHG in Earth's atmosphere, listed in decreasing order of average global mole fraction, are: water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Today, scientists around the world continue to try and solve the puzzle of climate change. It is clear that to address climate change, the amount of CO2 released into the atmosphere by industrial process has to be reduced because once it is added to the atmosphere, it can continue to affect climate for thousands of years. For such a purpose, an approach to intervention using expression vectors for any protein targeting to the cell plasma membrane via the glycosylphosphatidylinositol, GPI, anchor is suggested. The resulting GPI-anchored proteins would be useful for studying intermolecular interactions, especially gene-environment interactions, in investigating the potential impact of any chemical compounds on any genes of interest and could be used for carbonic anhydrase (CA)-based CO2-capture (environmental application). This approach would be crucial not only for capturing CO2 via GPI and CA but also for the production of CA enzyme as well as its stabilization and therefore useful for combating the global warming of climate change.

Encephalomalacia/gliosis, deep venous thrombosis, and cancer in Arg393His antithrombin Hanoi and the potential impact of the ß-amyloid precursor protein (APP) on thrombosis and cancer.

A heterozygous Arg393His point mutation at the reactive site of antithrombin (AT) gene causing thrombosis in a Vietnamese patient is reported and named as Arg393His in AT-Hanoi. The present variant is characterized by a severe reduction of functionally active AT plasma concentration to 42% of normal resulting in multiple severe thrombotic events such as cerebral venous thrombosis (CVT) (encephalomalacia/gliosis), recurrent deep venous thrombosis (DVT) and the development of kidney cancer. Today the complexity of thrombophilia has grown with appreciation that multiple inherited and acquired risk factors may interact to result in a clinically thrombotic phenotype. This article focuses on the following issues: (1) pathophysiology and clinical conditions of Arg393His in AT-Hanoi; (2) "two way association" between cancer and thrombosis in which venous thromboembolism (VTE) can be both a presenting sign and a complication of cancer; (3) efficacy of anticoagulants used for the prevention of cancer-related thrombosis; (4) conditions of acquired risk factors such as cancer or genetic disorders via epigenetic modifications in gene-gene (epistasis) and/or gene-environment interactions such as in Lesch-Nyhan disease (LND), in which the ß-amyloid precursor protein (APP) that may interact to predispose a patient to thrombosis and cancer. It is also necessary to study the hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme, AT, and APP using expression vectors for exploring their impact on LND, thrombosis as well as other human diseases, especially the ones related to APP such as Alzheimer's disease (AD) and cancer. For such a purpose, the construction of expression vectors for HGprt and APP, with or without the glycosyl-phosphatidylinositol (GPI) anchor, was performed as described in Ref. #148 (Nguyen, K. V., Naviaux, R. K., Nyhan, W. L. Lesch-Nyhan disease: I. Construction of expression vectors for hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme and amyloid precursor protein (APP). Nucleosides Nucleotides Nucleic Acids 2020, 39: 905-922). In the same manner, the construction of expression vectors for AT and APP can be performed as shown in Figure 6. These expressions vectors, with or without GPI anchor, could be used as tools for (a) studying the effects of Arg393His mutation in AT; (b) studying the emerging role of Arg393His mutation in AT and cancer; (c) studying intermolecular interactions between APP and AT. Furthermore, the construction of expression vectors as described in Ref. #148, especially the one with GPI, can be used as a model for the construction of expression vectors for any protein targeting to the cell plasma membrane for studying intermolecular interactions and could be therefore useful in the vaccines as well as antiviral drugs development (studying intermolecular interactions between the spike glycoprotein of the severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, as well as its variants and the angiotensin-converting enzyme 2, ACE2, in coronavirus disease 2019 (COVID-19) [155],[156], for example).

Containing the spread of COVID-19 virus facing to its high mutation rate: approach to intervention using a nonspecific way of blocking its entry into the cells.

Viruses have multiple mutation rates that are higher than any other member of the kingdom of life. This gives them the ability to evolve, even within the course of a single infection, and to evade multiple host defenses, thereby impacting pathogenesis. Additionally, there are also interplays between mutation and recombination and the high multiplicity of infection (MOI) that enhance viral adaptability and increase levels of recombination leading to complex and conflicting effects on genome selection, and the net results is difficult to predict. Recently, the outbreak of COVID-19 virus represents a pandemic threat that has been declared a public health emergency of international concern. Up to present, however, due to the high mutation rate of COVID-19 virus, there are no effective procedures to contain the spread of this virus across the globe. For such a purpose, there is then an urgent need to explore new approaches. As an opinion, the present approach emphasizes on (a) the use of a nonspecific way of blocking the entry of COVID-19 virus as well as its variants into the cells via a therapeutic biocompatible compound (ideally, "in a pill") targeting its spike (S) glycoprotein; and (b) the construction of expression vectors via the glycosyl-phosphatidylinositol, GPI, anchor for studying intermolecular interactions between the spike S of COVID-19 virus as well as its variants and the angiotensin-converting enzyme 2 (ACE2) of its host receptor for checking the efficacy of any therapeutic biocompatible compound of the nonspecific way of blocking. Such antiviral drug would be safer than the ACE1 and ACE2 inhibitors/angiotensin receptor blockers, and recombinant human ACE2 as well as nucleoside analogs or protease inhibitors used for fighting the spread of the virus inside the cells, and it would also be used as a universal one for any eventual future pandemic related to viruses, especially the RNA viruses with high mutation rates.

Potential molecular link between the ß-amyloid precursor protein (APP) and hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme in Lesch-Nyhan disease and cancer.

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorders of purine metabolic in which the cytoplasmic enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. Despite having been characterized over 60 years ago, however, up to now, there is no satisfactory explanation of how deficits in enzyme HGprt can lead to LND with the development of the persistent and severe self-injurious behavior. Recently, a role for epistasis between the mutated hypoxanthine phosphoribosyltransferase 1 (HPRT1) and the ß-amyloid precursor protein (APP) genes affecting the regulation of alternative APP pre-mRNA splicing in LND has been demonstrated. Furthermore, there were also some reported cases of LND developing thrombosis while APP is an important regulator of vein thrombosis and controls coagulation. Otherwise, the surface expression of HGprt enzyme was also observed in several somatic tissue cancers while APP and the APP-like protein-2 (APLP2) are deregulated in cancer cells and linked to increased tumor cell proliferation, migration, and invasion. The present review provides a discussion about these findings and suggests a potential molecular link between APP and HGprt via epistasis between HPRT1 and APP genes affecting the regulation of alternative APP pre-mRNA splicing. As a perspective, expression vectors for HGprt enzyme and APP are constructed as described in Ref. # 24 (Nguyen KV, Naviaux RK, Nyhan WL (2020) Lesch-Nyhan disease: I. Construction of expression vectors for hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme and amyloid precursor protein (APP). Nucleosides Nucleotides Nucleic Acids 39: 905-922), and they could be used as tools for clarification of these issues. In addition, these expression vectors, especially the one with the glycosyl-phosphatidylinositol (GPI) anchor can be used as a model for the construction of expression vectors for any protein targeting to the cell plasma membrane for studying intermolecular interactions and could be therefore useful in the vaccines as well as antiviral drugs development (studying intermolecular interactions between the spike glycoprotein of the severe acute respiratory syndrome coronavirus 2, SARS-CoV-2, as well as its variants and the angiotensin-converting enzyme 2, ACE2, in coronavirus disease 2019 (COVID-19) [43],[44], for example).

Problems associated with antiviral drugs and vaccines development for COVID-19: approach to intervention using expression vectors via GPI anchor.

The outbreak of a novel coronavirus responsible for the severe acquired respiratory syndrome: SARS-CoV-2, also known as coronavirus disease 2019: COVID-19, represents a pandemic threat that has been declared a public health emergency of international concern. The CoV spike (S) glycoprotein is a key target for diagnostic, development of antibodies, entry inhibitors, and vaccines. COVID-19 also recognizes angiotensin-converting enzyme 2 (ACE2) as its host receptor binding to viral S protein. Several antiviral drugs and vaccines have been evaluated for the treatment and prevention of the infection by the virus. To facilitate medical countermeasure development, the problems associated with antiviral drugs and vaccines development for containing the spread of COVID-19 are discussed. There is an urgent need to study deeply on the structure, mutations, and function of COVID-19 as well as its pathophysiology from a large population. Construction of expression vectors for any protein targeting to the cell plasma membrane via the glycosyl-phosphatidylinositol, GPI, anchor for studying intermolecular interactions, as described in Ref. # 62 (Nguyen, K. V., Naviaux, R. K., Nyhan, W. L. Lesch-Nyhan disease: I. Construction of expression vectors for hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme and amyloid precursor protein (APP). Nucleosides Nucleotides Nucleic Acids 2020, 39, 905-922), between the S protein of COVID-19 as well as its variants and ACE2 could be useful in antiviral drugs and vaccines development.

Lesch-Nyhan disease: I. Construction of expression vectors for hypoxanthine-guanine phosphoribosyltransferase (HGprt) enzyme and amyloid precursor protein (APP).

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. Despite having been characterized over 50 years ago, it remains unclear precisely how deficits in HGprt enzyme activity can lead to the neurological syndrome, especially the self-injury of LND. Several studies have proposed different hypotheses regarding the etiology of this disease, and several treatments have been tried in patients. However, up to now, there is no satisfactory explanation of the disease and for many LND patients, efficacious treatment for persistent self-injurious behavior remains unreachable. A role for epistasis between mutated hypoxanthine phosphoribosyltransferase 1 (HPRT1) and amyloid precursor protein (APP) genes has been recently suggested. This finding may provide new directions not only for investigating the role of APP in neuropathology associated with HGprt-deficiency in LND but also for the research in neurodevelopmental and neurodegenerative disorders in which the APP gene is involved in the pathogenesis of diseases and may pave the way for new strategies applicable to rational antisense drugs design. It is therefore necessary to study the HGprt enzyme and APP using expression vectors for exploring their impacts on LND as well as other human diseases, especially the ones related to APP such as Alzheimer's disease in which the physiologic function and the structure of the entire APP remain largely unclear until now. For such a purpose, we report here the construction of expression vectors as the first step (Part I) of our investigation.

Potential epigenomic co-management in rare diseases and epigenetic therapy.

The purpose of this review is to highlight the impact of the alternative splicing process on human disease. Epigenetic regulation determines not only what parts of the genome are expressed but also how they are spliced. The recent progress in the field of epigenetics has important implications for the study of rare diseases. The role of epigenetics in rare diseases is a key issue in molecular physiology and medicine because not only rare diseases can benefit from epigenetic research, but can also provide useful principles for other common and complex disorders such as cancer, cardiovascular, type 2 diabetes, obesity, and neurological diseases. Predominantly, epigenetic modifications include DNA methylation, histone modification, and RNA-associated silencing. These modifications in the genome regulate numerous cellular activities. Disruption of epigenetic regulation process can contribute to the etiology of numerous diseases during both prenatal and postnatal life. Here, I discuss current knowledge about this matter including some current epigenetic therapies and future directions in the field by emphasizing on the RNA-based therapy via antisense oligonucleotides to correct splicing defects.

ß-Amyloid precursor protein (APP) and the human diseases.

Several pathophysiological functions of the human ß-amyloid precursor protein (APP) have been recently proposed in different human diseases such as neurodevelopmental and neurodegenerative disorders including rare diseases such as autism, fragile X syndrome, amyotrophic lateral sclerosis, multiple sclerosis, Lesch-Nyhan disease; common and complex disorders such as Alzheimer's disease; metabolic disorders such as diabetes; and also cancer. APP as well as all of its proteolytic fragments including the amyloid-ß (Aß) peptide, are part of normal physiology. The targeting of the components of APP proteolytic processing as a pharmacologic strategy will not be without consequences. Recent research results highlight the impact of alternative splicing (AS) process on human disease, and may provide new directions for the research on the impact of the human APP on human diseases. The identification of molecules capable of correcting and/or inhibiting pathological splicing events is therefore an important issue for future therapeutic approaches. To this end, the defective APP-mRNA isoform responsible for the disease in cells and tissues appears as an ideal target for epigenetic therapeutic intervention and antisense drugs are potential treatment.

Special Issue: Alzheimer's disease.

More than 45 million people worldwide have Alzheimer's disease (AD), a deterioration of memory and other cognitive domains that leads to death within 3 to 9 years after diagnosis. The principal risk factor for AD is age. As the aging population increases, the prevalence will approach 131 million cases worldwide in 2050. AD is therefore a global problem creating a rapidly growing epidemic and becoming a major threat to healthcare in our societies. It has been more than 20 years since it was first proposed that the neurodegeneration in AD may be caused by deposition of amyloid-ß (Aß) peptides in plaques in brain tissue. According to the amyloid hypothesis, accumulation of Aß peptides, resulting from a chronic imbalance between Aß production and Aß clearance in the brain, is the primary influence driving AD pathogenesis. Current available medications appear to be able to produce moderate symptomatic benefits but not to stop disease progression. The search for biomarkers as well as novel therapeutic approaches for AD has been a major focus of research. Recent findings, however, show that neuronal-injury biomarkers are independent of Aß suggesting epigenetic modifications, gene-gene and/or gene-environment interactions in the disease etiology, and calling for reconsideration of the pathological cascade and assessment of alternative therapeutic strategies. In addition, recent research results regarding the expression of the ß-amyloid precursor protein (APP) gene resulting in the presence of various APP-mRNA isoforms and their quantification, especially for identifying the most abundant one that may decisive for the normal status or disease risk, have been reported. As such, a more complete understanding of AD pathogenesis will likely require greater insights into the physiological function of the ß-amyloid precursor protein (APP).

Novel mutation in the human HPRT1 gene and the Lesch-Nyhan disease.

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report a novel point mutation that led to HGprt-related neurological dysfunction (HND) in a family in which there was a missense mutation in exon 6 of the coding region of the HPRT1 gene: g.34938G>T, c.403G>T, p.D135Y. Molecular diagnosis is consistent with the genetic heterogeneity of the HPRT1 gene responsible for HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.

Lesch-Nyhan disease in two families from Chiloé Island with mutations in the HPRT1 gene.

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report two independent point mutations leading to splicing errors: IVS 2 +1G>A, c.134 +1G>A, and IVS 3 +1G>A, c.318 +1G>A in the hypoxanthine-phosphoribosyltransferase1 (HPRT1) gene which result in exclusion of exon 2 and exon 3 respectively, in the HGprt enzyme protein from different members of two Chiloé Island families. Molecular analysis has revealed the heterogeneity of genetic mutation of the HPRT1 gene responsible for the HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.

Quantification of various APP-mRNA isoforms and epistasis in Lesch-Nyhan disease.

The present work is the development of a simple and specific kinetic method based on RT-PCR technique coupled with direct sequencing for quantification of various amyloid precursor protein-mRNA isoforms (APP-mRNA isoforms) in biological samples, especially for identifying the most abundant one that may decisive for the normal status or disease risk. Application of this kinetic method to the Lesch-Nyhan disease (LND) was performed and results indicated an epistasis between mutated hypoxanthine phosphoribosyltransferase1 (HPRT1) and APP genes. APP-mRNA isoform of 624bp, with a deletion starting after 49bp of the 5' end of exon 3 followed by a complete deletion of exons 4-15, mutations in exon 1: c.22C>T, p.L18F, and exon 3: c.269A>G, p.Q90R encoding APP207 isoform, was the most abundant one in most of the LND patients and would be responsible for the neurobehavioral syndrome in these patients. The method is useful for identifying the defective APP-mRNA isoform in LND patients, and in neurodevelopmental and neurodegenerative disorders in which the APP gene is involved in the pathogenesis of diseases such as autism, fragile X syndrome, amyotrophic lateral sclerosis, and Alzheimer's disease, and may pave the way for new strategies applicable to rational antisense drugs design.

Human HPRT1 gene and the Lesch-Nyhan disease: Substitution of alanine for glycine and inversely in the HGprt enzyme protein.

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report three novel independent mutations in the coding region of the HPRT1 gene from genomic DNA of (a) a carrier sister of two male patients with LND: c.569G>C, p.G190A in exon 8; and (b) two LND affected male patients unrelated to her who had two mutations: c.648delC, p.Y216X, and c.653C>G, p.A218G in exon 9. Molecular analysis reveals the heterogeneity of genetic mutation of the HPRT1 gene responsible for the HGprt deficiency. It allows fast, accurate detection of carriers and genetic counseling.

A neurodevelopmental disorder with a nonsense mutation in the Ox-2 antigen domain of the amyloid precursor protein (APP) gene.

We report a patient, an infant with a neurodevelopmental disorder manifesting intractable complex partial epilepsy, bull's eye maculopathy, microcephaly, bilateral cataracts, truncal hypotonia, and spasticity of all four extremities. Sequencing of genomic DNA revealed mutations in (a) exon 8 (Ox-2 antigen domain) of the amyloid precursor protein (APP) gene: c.1075C>T, p.Arg359* (b) exon 8 of the senataxin (SETX) gene: c.4738C>T, p.Arg1580Cys, and (c) exon 2 of the ceroid-lipofuscinosis, neuronal 8 (CLN8) gene: c.685C>G, p.Pro229Ala. Using a quantitative method for measurement of various APP-mRNA isoforms, we found that the APP-mRNA isoform of 624 bp with a deletion starting after 49 bp of the 5' end of exon 3 followed by a complete deletion of exons 4-15, mutations in exon 1: c.22C>T, p.L18F, and exon 3: c.269A>G, p.Q90R encoding APP207 isoform was the most abundant one, and would appear to be responsible for the clinical manifestations. This is the first example that may underline the role of the epigenetic regulation in the expression of APP gene leading to a neurodevelopmental disorder resulting from a nonsense mutation in the Ox-2 antigen domain.

Mutation in the Human HPRT1 Gene and the Lesch-Nyhan Syndrome.

Lesch-Nyhan syndrome (LNS) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report a novel mutation which led to HGprt-related neurological dysfunction (HND) in two brothers from the same family with a missense mutation in exon 6 of the coding region of the HPRT1 gene: c.437T>C, p.L146S. Molecular diagnosis discloses the genetic heterogeneity of the HPRT1 gene responsible for HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.

Epigenetic Regulation in Amyloid Precursor Protein with Genomic Rearrangements and the Lesch-Nyhan Syndrome.

Recently, epigenetic regulation of alternative APP pre-mRNA splicing in the Lesch-Nyhan syndrome (LNS) has been studied (see Ref. 7) and showed for the first time, the presence of several APP-mRNA isoforms encoding divers APP protein isoforms ranging from 120 to 770 amino acids (with or without mutations and/or deletions). Here, by continuing on this work, I identified, for the first time new APP-mRNA isoforms with a deletion followed by an insertion (INDELS) in LNS and LNVs patients: c.19_2295delinsG166TT…GAGTCC…CTTAGTC…TCT489,p.Leu7Valfs*2;c.19_2295 delinsG169TT…GAGACC…CTTGGTC…TCT492,p.Leu7Valfs*2;and c.16_2313delinsG84CC…CAT616,p.Leu7Hisfs*45. A role of genomic rearrangements of APP gene via the Fork Stalling and Template Switching (FoSTeS) mechanism leading to INDELS was suggested. Epistasis between mutated HPRT1 and APP genes could be one of the factors of epigenetic modifications responsible for genomic rearrangements of APP gene. My findings accounted for epigenetic mechanism in the regulation of alternative APP pre-mRNA splicing as well as for epigenetic control of genomic rearrangements of APP gene may provide therefore new directions not only for investigating the role of APP in neuropathology associated with HGprt-deficiency in LNS and LNVs patients but also for the research in neurodevelopmental and neurodegenerative disorders by which APP gene involved in the pathogenesis of the diseases such as autism, fragile X syndrome (FXS), and Alzheimer's disease (AD) with its diversity and complexity, especially for sporadic form of AD (SAD). An accurate quantification of various APP-mRNA isoforms in brain tissues for detection of initial pathological changes or pathology development is needed and antisense drugs are the potential treatments.

Lesch-Nyhan Syndrome in a Family with a Deletion Followed by an Insertion within the HPRT1 Gene.

Lesch-Nyhan syndrome (LNS) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase(HGprt) is defective. The authors report a novel mutation which led to LNS in a family with a deletion followed by an insertion (INDELS) via the serial replication slippage mechanism: c.428_432delTGCAGinsAGCAAA, p.Met143Lysfs*12 in exon 6 of HPRT1 gene. Molecular diagnosis discloses the genetic heterogeneity of HPRT1 gene responsible for HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.

The human ß-amyloid precursor protein: biomolecular and epigenetic aspects.

Beta-amyloid precursor protein (APP) is a membrane-spanning protein with a large extracellular domain and a much smaller intracellular domain. APP plays a central role in Alzheimer's disease (AD) pathogenesis: APP processing generates ß-amyloid (Aß) peptides, which are deposited as amyloid plaques in the brains of AD individuals; point mutations and duplications of APP are causal for a subset of early-onset familial AD (FAD) (onset age <65 years old). However, these mutations in FAD represent a very small percentage of cases (∼1%). Approximately 99% of AD cases are nonfamilial and late-onset, i.e., sporadic AD (SAD) (onset age >65 years old), and the pathophysiology of this disorder is not yet fully understood. APP is an extremely complex molecule that may be functionally important in its full-length configuration, as well as the source of numerous fragments with varying effects on neural function, yet the normal function of APP remains largely unknown. This article provides an overview of our current understanding of APP, including its structure, expression patterns, proteolytic processing and putative functions. Importantly, and for the first time, my recent data concerning its epigenetic regulation, especially in alternative APP pre-mRNA splicing and in the control of genomic rearrangements of the APP gene, are also reported. These findings may provide new directions for investigating the role of APP in neuropathology associated with a deficiency in the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGprt) found in patients with Lesch-Nyhan syndrome (LNS) and its attenuated variants (LNVs). Also, these findings may be of significance for research in neurodevelopmental and neurodegenerative disorders in which the APP gene is involved in the pathogenesis of diseases such as autism, fragile X syndrome (FXS) and AD, with its diversity and complexity, SAD in particular. Accurate quantification of various APP-mRNA isoforms in brain tissues is needed, and antisense drugs are potential treatments.

Epigenetic regulation in amyloid precursor protein and the Lesch-Nyhan syndrome.

Lesch-Nyhan syndrome (LNS) is a neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HPRT) is defective. A major unsolved question is how the loss of HPRT enzyme function affects the brain to cause the neurobehavioural syndrome in LNS and its attenuated variants (LNVs). To address this issue, a search for a link between LNS and the amyloid precursor protein (APP) is developed. Here, I identified, for the first time in fibroblasts from normal subjects as well as from LNS and LNV patients: (a) several APP-mRNA isoforms encoding divers APP protein isoforms ranging from 120 to 770 amino acids (with or without mutations and/or deletions) accounted for epigenetic mechanisms in the regulation of alternative APP pre-mRNA splicing and (b) five novel independent polymorphisms in the APP promoter: -956A>G, -1023T>C, -1161A>G, -2224G>A, -2335C>T relative to the transcription start site. A role for epistasis between mutated HPRT and APP genes affecting the regulation of alternative APP pre-mRNA splicing in LNS is suggested. An accurate quantification of various APP isoforms in brain tissues for detection of initial pathological changes or pathology development is needed. My findings may provide new directions not only for investigating the role of APP in neuropathology associated with HPRT-deficiency in LNS but also for the research in neurodevelopmental and neurodegenerative disorders by which various APP isoforms involved in the pathogenesis of the diseases such as Alzheimer's disease.

Identification of novel mutations in the human HPRT gene.

Inherited mutation of the purine salvage enzyme, hypoxanthine guanine phosphoribosyltransferase (HPRT) gives rise to Lesch-Nyhan syndrome (LNS) or Lesch-Nyhan variants (LNVs). We report three novel independent mutations in the coding region of HPRT gene: exon 3: c.141delA, p.D47fs53X; exon 5: c.400G>A, p.E134K; exon 7: c.499A>G, p.R167G from three LNS affected male patients.