HOGA1 Gene Research Articles

Effective Newborn Screening for Type 1 and 3 Primary Hyperoxaluria

IntroductionNewborn Screening programs for a defined set of eligible diseases have been enormously successful, but genomic newborn screening allowing for detection of additional treatable disorders has not been broadly implemented. All three types of primary hyperoxaluria (PH1-3) are rare autosomal recessive diseases caused by distinct defects of glyoxylate metabolism that are diagnosed genetically with certainty. Early diagnosis and treatment are mandatory to avoid renal failure or sequalae associated with persistent hyperoxaluria. MethodsThe prospective pilot study was undertaken within the framework of the German Newborn Screening. DNA samples extracted from dried blood spot cards were screened by multiplex PCR for the two most prevalent mutations: AGXT c.508G>A (PH1) and HOGA1 c.700+5G>T (PH3). Heterozygous AGXT/HOGA1 carriers received repeated spot urine analyses and, in case of persistent hyperoxaluria, complete Sanger sequencing of AGXT and HOGA1 gene, respectively. ResultsBetween March 15th 2022 and June 30th 2023 additional screening for PH1 and PH3 was performed in 77199 out of 222638 newborns included in the regular newborn screening program. No homozygous individuals, but 274 potential carriers for the AGXT mistargeting and 287 potential carriers for the HOGA1 splice variant were identified. Further work up revealed two already symptomatic compound heterozygous infants, one with PH1 (genotype c.508G>A; c.33delC) and one with PH3 (genotype: c.700+5G>T;c.134C>G). A second symptomatic PH1 patient (father of an identified carrier; genotype: c.508G>A;c.508G>A) was uncovered via family history. ConclusionThis pilot study demonstrated the efficacy of a genomic neonatal screening program for primary hyperoxaluria even in relatively small cohorts.

HOGA1 variants in Chinese patients with primary hyperoxaluria type 3: genetic features and genotype-phenotype relationships.

The aim of our study is to describe the genetic features and correlation between the genotype and phenotype of Chinese patients with primary hyperoxaluria type 3 (PH3). The genetic and clinical data of PH3 patients in our cohort were collected and analyzed retrospectively. All published studies of Chinese PH3 populations between January 2010 and November 2022 were searched and enrolled based on inclusive standards. A total of 60 Chinese PH3 patients (21 cases from our cohort and 39 cases from previous studies) were included. The mean age of onset was 1.62 ± 1.35 (range 0.4-7) years. A total of 29 different variants in the HOGA1 gene were found. The mutations were most commonly clustered in exons 1, 6, and 7. Among the genotypes, exon 6 skipping (c.834G > A and c.834_834 + 1GG > TT mutations) was the most common, followed by c.769T > G; the allele frequencies (AFs) were 48.76% and 12.40%, respectively. Patients homozygous for exon 6 skipping exhibited a median age of onset of 0.67 (0.58-1) years, which was significantly lower than that observed among heterozygotes and nonexon 6 skipping patients (p = 0.021). A total of 22.5% (9/40) of PH3 patients had a decreased estimated glomerular filtration rate, and one patient with homozygous exon 6 skipping developed end-stage renal disease. A hotspot mutation, potential hotspot mutation and genotype-phenotype correlation were found in Chinese PH3 patients. This study expands the mutational spectrum and contributes to the understanding of genotypic profiles of PH3, which may provide a potential diagnostic and therapeutic target.

Primary hyperoxaluria: Comprehensive mutation screening of the disease causing genes and spectrum of disease-associated pathogenic variants.

The primary hyperoxalurias are rare disorders of glyoxylate metabolism. Accurate diagnosis is essential for therapeutic and management strategies. We conducted a molecular study on patients suffering from recurrent calcium-oxalate stones and nephrocalcinosis and screened primary hyperoxaluria causing genes in a large cohort of early-onset cases. Disease-associated pathogenic-variants were defined as missense, nonsense, frameshift-indels, and splice-site variants with a reported minor allele frequency <1% in controls. We found pathogenic-variants in 34% of the cases. Variants in the AGXT gene causing PH-I were identified in 81% of the mutation positive cases. PH-II-associated variants in the GRHPR gene are found in 15% of the pediatric PH-positive population. Only 3% of the PH-positive cases have pathogenic-variants in the HOGA1 gene, responsible to cause PH-III. A population-specific AGXT gene variant c.1049G>A; p.Gly350Asp accounts for 22% of the PH-I-positive patients. Pathogenicity of the identified variants was evaluated by in-silico tools and ACMG guidelines. We have devised a rapid and low-cost approach for the screening of PH by using targeted-NGS highlighting the importance of an accurate and cost-effective screening platform. This is the largest study in Pakistani pediatric patients from South-Asian region that also expands the mutation spectrum of the three known genes.

Extended genetic analysis of exome sequencing for primary hyperoxaluria in pediatric urolithiasis patients with hyperoxaluria

Next generation sequencing-based exome sequencing can be used to identify genetic abnormalities in patients believed to be suffering from primary hyperoxaluria. We outline our efforts to improve the diagnostic capacity of exome sequencing for these patients. We conducted a retrospective analysis of exome sequencing data from 77 pediatric urolithiasis patients with hyperoxaluria of unknown origin. Canonical exome sequencing analysis was performed to identify pathogenic variants in three known primary hyperoxaluria-related genes (AGXT, GRHPR, HOGA1) as per the guidelines of the American College of Medical Genetics. Then, extended exome sequencing analyses of 5'-untranslated region, non-canonical splicing site and copy number variant were performed on patients with negative diagnostic results in these three genes. Canonical exome sequencing analyses led to the diagnosis of primary hyperoxaluria in 20/77 (26%) patients, including eight, four, and eight patients diagnosed with type 1, 2 and 3 primary hyperoxaluria, respectively. Non-canonical splicing site analyses discovered a pathogenic variant in the HOGA1 gene, which led to the diagnosis of six additional patients with type 3 primary hyperoxaluria, while copy number variant analyses from exome sequencing data identified a 1.8 kb copy number loss that impacted the AGXT gene, resulting in the diagnosis of an additional type 1 primary hyperoxaluria case. Extended non-canonical splicing site and copy number variant analyses improve the diagnostic yield of canonical exome sequencing analysis for primary hyperoxaluria from 26% (20/77) to 35% (27/77) in 77 pediatric urolithiasis patients with hyperoxaluria.

Characteristics of genotype of monogenic nephrolithiasis in Chinese pediatric patients with nephrolithiasis

Objective: To analyze the genotype characteristics of children with monogenic nephrolithiasis. Methods: The clinical data and genetic test results of 56 children with monogenic nephrolithiasis diagnosed and treated in Beijing Friendship Hospital, Capital Medical University from January 2016 to December 2020 were analyzed retrospectively. All pediatric patients were diagnosed by whole exome sequencing, and the genotype characteristics of the children were analyzed. Results: Among 56 children with monogenic nephrolithiasis, there were 39 males and 17 females, with an average age of 4 years (range, 5 months to 14 years). A total of 11 genes were found to have mutations, including 7 autosomal recessive genes, 1 X-linked recessive gene, and 3 genes with both recessive and dominant, of which HOGA1 gene mutation was the most common (16 cases, 28.6%), followed by AGXT gene (15 cases, 26.8%), SLC3A1 gene (6 cases, 10.7%), SLC7A9 gene (5 cases, 8.9%) and GRHPR gene (5 cases, 8.9%). The mutation types included nonsense mutations, frameshift mutations and splicing mutations, with 14 novel mutations. Genes such as AGXT, GRHPR and HOGA1 have hotspot mutations or hotspot mutation regions, which are c. 815-816 insGA and c. 33dupC mutation, c.864-865delTG mutation and c. 834-834+1 mutation region; SLC3A1 and SLC7A9 genes had 9 novel mutations, but no hotspot mutation or hotspot regions were found. Conclusion: Monogenic nephrolithiasis is rare and mostly autosomal recessive in Chinese children, with mutations in the causative genes HOGA1, AGXT, SLC3A1,SLC7A9 and GRHPR. AGXT, GRHPR and HOGA1 genes have hotspot mutations or hotspot mutation regions, and mutations may have ethnic differences.

Possible ethnic associations in primary hyperoxaluria type-III-associated HOGA1 sequence variants.

Primary hyperoxaluria type-III is a disorder of glyoxylate metabolism, caused by pathogenic variants in the HOGA1 gene. To date more than 50 disease-associated pathogenic sequence variants are identified in the gene. A few of the variants are population specific and are considered to have a founder effect in respective populations. The most prevalent variant, c.700+5G>T, identified frequently in Caucasian (allele frequency 0.63) and European (0.35) populations. Two variants, c.860G>T (p.Gly287Val) and c.944_946delAGG (p.Glu315del), account for 95% of the allele count in patients of Ashkenazi Jews ancestry. A possible mutational hot-spot at c.834 position is frequently found mutated in Chinese patients. This observed ethnic associations of HOGA1 alleles span a spectrum ranging from recurrence limited to an ethnic group to a possible founder-effect.

P0172ARE FREQUENT STONE REMOVAL PROCEDURES IN PATIENTS WITH PRIMARY HYPEROXALURIA TYPE 3 (PH 3) RELATED TO DECLINE IN KIDNEY FUNCTION?

Abstract Background and Aims PHIII is seen as the less problematic type of autosomal recessive inherited PH. This group of disorders in glyoxylate metabolism is clinically characterized by recurrent urolithiasis and/or progressive nephrocalcinosis, and, in type I and II, end-stage renal failure. The cause of PHIII was identified only in 2010 and unlike in PHI/II a remarkable low prevalence of symptomatic adults was observed, hence long-term clinical data are scarce. This phenomenon is commonly attributed to reduced penetrance of causative hydroxy-oxo-glutarate aldolase 1 gene (HOGA1) variants and a still unexplained tendency for clinical remission with age. Most PHIII patients present in early childhood with recurrent urolithiasis and undergo (repeated) stone removal procedures. We now hypothesized that repeated stone removal procedures may be associated with decline in kidney function. Method We retrospectively analyzed clinical and laboratory data of 41 genetically confirmed PHIII patients (0.5-29.3 years of age, with (20 different) biallelic mutations in the HOGA1 gene). Period of follow-up ranged from just diagnosed to 22 years. Results Recurrent urolithiasis was most prominently found in the first 3 years of life (&amp;gt;25% of patients). Not all patients experienced clinical remission, 3/6 patients &amp;gt; 20 years of age have ongoing kidney stone development. In addition, patients presented with nephrocalcinosis and/or urolithiasis. A high amount of stone removal procedures during the first years, but also later in life was observed. Urinary oxalate excretion is significantly elevated, and within the range of PHI/II. A decline in kidney function was observed, which is related to a decreased clearance of oxalate (figure). Two patients each post multiple stone removal procedures had CKD stages 2 or 3. Seven further patients had CKD stage 2, which was not related to stone removal. Conclusion PHIII is said to be the most favorable PH type, but early diagnosis is mandatory to treat the patients adequately and to avoid repeated stone removal procedures, which may have an influence on decline in kidney function. This decline may also be related to hyperoxaluria per se, as reported for PHI and II.

Mutational analysis of HOGA1 gene in Chinese pediatric patients with primary hyperoxaluria type 3

Primary hyperoxaluria type 3(PH3) is an autosomal recessive metabolic disorder caused by inherited mutations in the HOGA1 gene. Nearly thirty HOGA1 mutations have been reported in PH3 with c.700+5G>T accounting for about 50% of the total alleles in the literatures. The aim of our study was to analyze and characterize the mutational spectrum of PH3 in Chinese pediatric patients with kidney stones. Ninety-five pediatric patients with early-onset nephrolithiasis were suspected of having PH. We searched for HOGA1 gene mutations in the patients and their parents. The whole exome sequencing were performed, the approach was confirmed by Sanger sequencing. PH3 were found in 14 pediatric patients respectively. Among of PH3 patients,10 were boys and 4 were girls, the mean age was 28 months. The most commonly mutation was seen in 9 patients, which was a guanine to adenine substitution of the last nucleotide of exon (c.834G>A). Three boys and one girl are heterozygous c.834_834+1GG>TT and c.834G>A (p.A278A) mutations. This is the largest cases reporting PH3 mutations in Chinese pediatric patients. A few novel HOGA1 mutations were found in associated with PH3, and the potential hot spots of mutation (c.834_834+1) were found in the Chinese pediatric patients with kidney stones. Future investigation in Chinese pediatric populations, especially cases with PH3 genotype and phenotype, are highly needed.

Primary Hyperoxaluria in Korean Pediatric Patients

Background Primary hyperoxaluria (PH), a rare inborn error of glyoxylate meta bolism causing overproduction of oxalate, is classified into three genetic subgroups: type 1–3 (PH1–PH3) caused by AGXT, GRHPR, and HOGA1 gene mutations, respectively. We performed a retrospective case series study of Korean pediatric patients with PH. Methods In total, 11 unrelated pediatric patients were recruited and their phenotypes and genotypes were analyzed by a retrospective review of their medical records. Results Mutational analyses revealed biallelic AGXT mutations (PH1) in nine patients and a single heterozygous GRHPR and HOGA1 mutation in one patient each. The c.33dupC was the most common AGXT mutation with an allelic frequency of 44%. The median age of onset was 3 months (range, 2 months–3 years), and eight patients with PH1 presented with end stage renal disease (ESRD). Patients with two truncating mutations showed an earlier age of onset and more frequent retinal involvement than patients with one truncating mutation. Among eight PH1 patients presenting with ESRD, five patients were treated with intensive dialysis followed by liver transplantation (n=5) with/without subsequent kidney transplantation (n=3). Conclusion Most patients presented with severe infantile forms of PH. Patients with two truncating mutations displayed more severe phenotypes than those of patients with one truncating mutation. Sequential liver and kidney transplantation was adopted for PH1 patients presenting with ESRD. A larger nation-wide multicenter study is needed to confirm the genotype-phenotype correlations and outcomes of organ transplantation. Key words: Primary hyperoxaluria, AGXT gene, End stage renal disease, Genotype-phenotype correlation, Liver transplantation, Kidney transplantation

Nine novel HOGA1 gene mutations identified in primary hyperoxaluria type 3 and distinct clinical and biochemical characteristics in Chinese children.

Primary hyperoxaluria type 3 (PH3) is characterized by mutations in the 4-hydroxy-2-oxoglutarate aldolase (HOGA1) gene. PH3 patients are thought to present with a less severe phenotype than PH1 and PH2 patients. However, the clinical characteristics of PH3 patients have yet to be defined in sufficient detail. The aims of this study were to report HOGA1 mutations of PH3 in Chinese children, and to analyze the genotype and clinical characteristics of these PH3 patients. Genetic analysis (targeted gene panel-based and/or whole-exome sequencing) of HOGA1 was performed in 52 patients with a high suspicion of PH3, and DNA was obtained from the patient and both the parents. The clinical, biochemical, and genetic data of these 12 patients identified with HOGA1 mutations were subsequently retrospectively reviewed. These 12 patients were identified with HOGA1 mutation. The median onset of clinical symptoms was 18.25 (range 5-38) months. In total, 14 different mutations were identified including 9 novel mutations in these 12 patients with PH3. All of these 12 patients initially presented with urolithiasis, and 3 patients among them comorbid urinary tract infection (UTI) as another initial symptom. Ten patients experienced hyperoxaluria (average oxalate 0.77mmol/1.73m2/24h). In contrast, urine calcium excretion was normal in 8 patients and 2 patients with hypercalciuria (urine calcium > 4mg/kg/24h). At the time of diagnosis, estimated GFR was 155.6ml/min per 1.73m2, and at last follow-up time (17.3months later from diagnosis on average), estimated GFR was 157.5ml/min per 1.73m2. To date, none of the patients has impaired renal function based on and progressed to ESRD. We found that PH3 was significantly diagnosed in our urolithiasis patients during childhood. Nine novel HOGA1 mutations were identified in association with PH3, which provide a first-line investigation in Chinese PH3 patients. The eGFR was normal in all children with PH3. This finding is in contrast to the early impairment of renal function in PH1 and PH2.

MP03-15 MUTATIONAL ANALYSIS OF HOGA1 IN CHINESE PEDIATRIC PATIENTS WITH PRIMARY HYPEROXALURIA TYPE 3

INTRODUCTION AND OBJECTIVES:Primary hyperoxaluria type 3(PH3) is an autosomal recessive metabolic disorder caused by inherited mutations in the HOGA1 gene. Nearly thirty HOGA1 mutations have been r...

Mutation Hot Spot Region in the HOGA1 Gene Associated with Primary Hyperoxaluria Type 3 in the Chinese Population

Background: Primary hyperoxaluria type 3 (PH3) is a rare autosomal recessive disorder that affects glyoxylate metabolism. PH3 is caused by defects in 4-hydroxy-2-oxoglutarate aldolase, which is encoded by the HOGA1 gene. However, only 3 cases of PH3 have been described in Asians until today. This study aimed to determine the clinical and mutation spectra of patients from mainland China with PH3. Methods: We applied targeted next-generation sequencing to four non-consanguineous, unrelated Chinese families with PH3 to identify the genes hosting disease-causing mutations. This approach was confirmed by Sanger sequencing. Results: Five patients (2 boys and 3 girls) from four unrelated Chinese families were admitted because of kidney stones. Five HOGA1 gene sequence mutations were detected, including two novel mutations, c.811C>T (p.R271C) and c.812G>A (p.R271H). These compound heterozygous mutations were detected in a female PH3 patient (patient 4). Other patients included 2 boys who had heterozygous c.834_834+1GG>TT and c.834G>A (p.A278A) mutations (patients 1 and 2), a girl with homozygous c.834G>A (p.A278A) mutation (patient 3), and a girl with heterozygous c.834_834+1GG>TT and c.346C>T (p.Q116X) mutations (patient 5). The mutations in the c.834_834+1 region, including c.834G>A, c.834+1G>T, and c.834_834+1GG>TT, account for 5/8 of alleles in our study and 3/4 of alleles reported among Chinese patients. All patients in this study received hyperhydration and urine alkalinization treatment. Conclusion: Five PH3 cases were reported. Potential mutation hot spot region (c.834_834+1) in the Chinese population and two novel mutations were found.

Metabolite diagnosis of primary hyperoxaluria type 3

Primary hyperoxaluria type 3 (PH3) is a recently described cause of childhood renal calculi. It results from mutations in the HOGA1 gene and most cases have been diagnosed after clinical ascertainment, exclusion of other genetic hyperoxalurias and mutation testing. Metabolite testing has not been widely applied but holds promise for the rapid screening and diagnosis of patients who are not specifically suspected to have PH3. Two cases presented with renal calculi. Urine metabolite testing by tandem mass spectrometry was performed as part of the routine diagnostic work-up for this condition. Both had significantly increased levels of the PH3 urine marker 4-hydroxyglutamate and related metabolites. The diagnosis of PH3 was confirmed by the finding of bi-allelic damaging HOGA1 mutations. Urine screening by tandem mass spectrometry is a rapid, high-throughput test that can detect PH3 cases that may otherwise not be diagnosed.

Hydroxyproline metabolism in a mouse model of Primary Hyperoxaluria Type 3

Primary Hyperoxaluria Type 3 is a recently discovered form of this autosomal recessive disease that results from mutations in the gene coding for 4-hydroxy-2-oxoglutarate aldolase (HOGA1). This enzyme is one of the 2 unique enzymes in the hydroxyproline catabolism pathway. Affected individuals have increased urinary excretions of oxalate, 4-hydroxy-L-glutamate (4-OH-Glu), 4-hydroxy-2-oxoglutarate (HOG), and 2,4-dihydroxyglutarate (DHG). While 4-OH-Glu and HOG are precursor substrates of HOGA1 and increases in their concentrations are expected, how DHG is formed and how HOG to oxalate are unclear. To resolve these important questions and to provide insight into possible therapeutic avenues for treating this disease, an animal model of the disease would be invaluable. We have developed a mouse model of this disease which has null mutations in the Hoga1 gene and have characterized its phenotype. It shares many characteristics of the human disease, particularly when challenged by the inclusion of hydroxyproline in the diet. An increased oxalate excretion is not observed in the KO mice which may be consistent with the recent recognition that only a small fraction of the individuals with the genotype for HOGA deficiency develop PH.

Two Novel HOGA1 Splicing Mutations Identified in a Chinese Patient with Primary Hyperoxaluria Type 3

Background: Twenty-six HOGA1 mutations have been reported in primary hyperoxaluria (PH) type 3 (PH3) patients with c.700 + 5G>T accounting for about 50% of the total alleles. However, PH3 has never been described in Asians. Methods: A Chinese child with early-onset nephrolithiasis was suspected of having PH. We searched for AGXT, GRHPR and HOGA1 gene mutations in this patient and his parents. All coding regions, including intron-exon boundaries, were analyzed using PCR followed by direct sequence analysis. Results: Two heterozygous mutations not previously described in the literature about HOGA1 were identified (compound heterozygous). One mutation was a successive 2 bp substitution at the last nucleotide of exon 6 and at the first nucleotide of intron 6, respectively (c.834_834 + 1GG>TT), while the other one was a guanine to adenine substitution of the last nucleotide of exon 6 (c.834G>A). Direct sequencing analysis failed to find these mutations in 100 unrelated healthy subjects and the functional role on splicing of both variants found in this study was confirmed by a minigene assay based on the pSPL3 exon trapping vector. In addition, we found a SNP in this family (c.715G>A, p.V239I). There were no mutations detected in AGXT and GRHPR. Conclusion: Two novel HOGA1 mutations were identified in association with PH3. This is the first description and investigation on mutant gene analysis of PH3 in an Asian.

Novel findings in patients with primary hyperoxaluria type III and implications for advanced molecular testing strategies

Identification of mutations in the HOGA1 gene as the cause of autosomal recessive primary hyperoxaluria (PH) type III has revitalized research in the field of PH and related stone disease. In contrast to the well-characterized entities of PH type I and type II, the pathophysiology and prevalence of type III is largely unknown. In this study, we analyzed a large cohort of subjects previously tested negative for type I/II by complete HOGA1 sequencing. Seven distinct mutations, among them four novel, were found in 15 patients. In patients of non-consanguineous European descent the previously reported c.700+5G>T splice-site mutation was predominant and represents a potential founder mutation, while in consanguineous families private homozygous mutations were identified throughout the gene. Furthermore, we identified a family where a homozygous mutation in HOGA1 (p.P190L) segregated in two siblings with an additional AGXT mutation (p.D201E). The two girls exhibiting triallelic inheritance presented a more severe phenotype than their only mildly affected p.P190L homozygous father. In silico analysis of five mutations reveals that HOGA1 deficiency is causing type III, yet reduced HOGA1 expression or aberrant subcellular protein targeting is unlikely to be the responsible pathomechanism. Our results strongly suggest HOGA1 as a major cause of PH, indicate a greater genetic heterogeneity of hyperoxaluria, and point to a favorable outcome of type III in the context of PH despite incomplete or absent biochemical remission. Multiallelic inheritance could have implications for genetic testing strategies and might represent an unrecognized mechanism for phenotype variability in PH.