Genotype-phenotype Correlation Research Articles

ATP1A3 Disease Spectrum Includes Paroxysmal Weakness and Encephalopathy Not Triggered by Fever.

Heterozygous pathogenic variants in ATP1A3, which encodes the catalytic alpha subunit of neuronal Na+/K+-ATPase, cause primarily neurologic disorders with widely variable features that can include episodic movement deficits. One distinctive presentation of ATP1A3-related disease is recurrent fever-triggered encephalopathy. This can occur with generalized weakness and/or ataxia and is described in the literature as relapsing encephalopathy with cerebellar ataxia. This syndrome displays genotype-phenotype correlation with variants at p.R756 causing temperature sensitivity of ATP1A3. We report clinical and in vitro functional evidence for a similar phenotype not triggered by fever but associated with protein loss-of-function. We describe the phenotype of an individual with de novo occurrence of a novel heterozygous ATP1A3 variant, NM_152296.5:c.388_390delGTG; p.(V130del). We confirmed the pathogenicity of p.V130del by cell survival complementation assay in HEK293 cells and then characterized its functional impact on enzymatic ion transport and extracellular sodium binding by two-electrode voltage clamp electrophysiology in Xenopus oocytes. To determine whether variant enzymes reach the cell surface, we surface-biotinylated oocytes expressing N-tagged ATP1A3. The proband is a 7-year-old boy who has had 2 lifetime episodes of paroxysmal weakness, encephalopathy, and ataxia not triggered by fever. He had speech regression and intermittent hand tremors after the second episode but otherwise spontaneously recovered after episodes and is at present developmentally appropriate. The p.V130del variant was identified on clinical trio exome sequencing, which did not reveal any other variants possibly associated with the phenotype. p.V130del eliminated ATP1A3 function in cell survival complementation assay. In Xenopus oocytes, p.V130del variant Na+/K+-ATPases showed complete loss of ion transport activity and marked abnormalities of extracellular Na+ binding at room temperature. Despite this clear loss-of-function effect, surface biotinylation under the same conditions revealed that p.V130del variant enzymes were still present at the oocyte's cell membrane. This individual's phenotype expands the clinical spectrum of ATP1A3-related recurrent encephalopathy to include presentations without fever-triggered events. The total loss of ion transport function with p.V130del, despite enzyme presence at the cell membrane, indicates that haploinsufficiency can cause relatively mild phenotypes in ATP1A3-related disease.

Exome sequencing in four families with neurodevelopmental disorders: genotype-phenotype correlation and identification of novel disease-causing variants in VPS13B and RELN.

Neurodevelopmental disorders (NDDs) are a clinically and genetically heterogeneous group of early-onset pediatric disorders that affect the structure and/or function of the central or peripheral nervous system. Achieving a precise molecular diagnosis for NDDs may be challenging due to the diverse genetic underpinnings and clinical variability. In the current study, we investigated the underlying genetic cause(s) of NDDs in four unrelated Pakistani families. Using exome sequencing (ES) as a diagnostic approach, we identified disease-causing variants in established NDD-associated genes in all families, including one hitherto unreported variant in RELN and three recurrent variants in VPS13B, DEGS1, and SPG11. Overall, our study highlights the potential of ES as a tool for clinical diagnosis.

Molecular and Clinical Features of Congenital Hypothyroidism due to Multiple DUOX2 Variants.

Background: DUOX2 is one of the major causative genes of congenital hypothyroidism (CH). Still, the mutation spectrum and clinical outcomes of biallelic DUOX2 variants are not fully understood. This study aimed to elucidate the molecular features and long-term clinical manifestations of CH caused by multiple pathogenic DUOX2 variants. Methods: A total of 255 patients with CH were screened for rare variants of 11 known causative genes. DUOX2 variants were classified according to their protein structure and residual activity. In vitro assays were performed for several variants of unknown function. Clinical analyses were conducted for patients with multiple pathogenic variants of DUOX2 but not of other genes. Results: We identified 24 pathogenic variants of DUOX2, together with two benign variants and seven variants of uncertain significance, in 63 patients. The pathogenic variants included three missense substitutions and one frameshift variant that have not been linked to CH. Twenty-one patients carried multiple pathogenic DUOX2 variants without any other pathogenic gene variants. Three of the 21 patients harbored homozygous variants. Family analysis, long-read amplicon sequencing, and haplotype phasing confirmed compound heterozygosity of the DUOX2 variants in 14 patients, whereas the allelic positions of the variants in the remaining four patients could not be determined. Of the 21 patients, 19 were treated with levothyroxine; their ages at drug withdrawal ranged from 9 months to 21.4 years. Three patients required retreatment after drug-free intervals of 6 months, 8 months, and 10 years. There were no differences in the clinical severity among patients with DUOX2 amorphic/amorphic, amorphic/hypomorphic, and hypomorphic/hypomorphic variants. Conclusions: These results broaden the mutation spectrum of DUOX2. Furthermore, our data imply that patients with multiple pathogenic DUOX2 variants typically exhibit transient CH without significant genotype-phenotype correlations. Most importantly, this study demonstrated for the first time that these patients are at risk of developing recurrent hypothyroidism after a long drug-free interval.

DEPDC5 plays a vital role in epilepsy: Genotypic and phenotypic features in cohort and literature.

DEPDC5 emerges to play a vital role in focal epilepsy. However, genotype-phenotype correlation in DEPDC5-related focal epilepsies is challenging and controversial. In this study, we aim to investigate the genotypic and phenotypic features in DEPDC5-affected patients. Genetic testing combined with criteria published by the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP), was used to identify pathogenic/likely pathogenic variants in DEPDC5 among the cohort of 479 patients with focal epilepsy. Besides, the literature review was performed to explore the genotype-phenotype correlation and the penetrance in DEPDC5-related focal epilepsies. Eight unrelated probands were revealed to carry different pathogenic/likely pathogenic variants in DEPDC5 and the total prevalence of DEPDC5-related focal epilepsy was 1.67% in the cohort. Sixty-five variants from 28 studies were included in our review. Combined with the cases reported, null variants accounted for a larger proportion than missense variants and were related to unfavorable prognosis (drug resistance or even sudden unexpected death in epilepsy; χ2 = 5.429, p = .020). And, the prognosis of probands with developmental delay/intellectual disability or focal cortical dysplasia was worse than that of probands with simple epilepsy (χ2 = -, p = .006). Besides, the overall penetrance of variants in DEPDC5 was 68.96% (231/335). The study expands the variant spectrum of DEPDC5 and proves that the DEPDC5 variant plays a significant role in focal epilepsy. Due to the characteristics of phenotypic heterogeneity and incomplete penetrance, genetic testing is necessary despite no specific family history. And we propose to adopt the ACMG/AMP criteria refined by ClinGen Sequence Variant Interpretation Working Group, for consistency in usage and transparency in classification rationale. Moreover, we reveal an important message to clinicians that the prognosis of DEPDC5-affected patients is related to the variant type and complications.

Case report: Exploring autosomal recessive woolly hair: genetic and scanning electron microscopic perspectives on a Japanese patient

Woolly hair (WH) is a hair shaft anomaly characterized by tightly curled hair that typically stops growing at a few inches. Autosomal recessive WH (ARWH; OMIM no. 278150/604379/616760) has been reported to be caused by variants in genes coding lysophosphatidic acid receptor 6 (LPAR6), lipase H (LIPH), or keratin 25 (KRT25). In this study, we conducted a scanning electron microscopic (SEM) examination of the hair of a 3-year-old Japanese ARWH patient. The SEM revealed that her affected hair had an irregular and rough cuticle compared to her mother’s hair. Many irregular small projections and longitudinal grooves were seen on the surface of the patient’s hair shaft, and some free margins of the hair cortex were raised or serrated. Her hairs were oval-shaped on the cross-section. Mutation analysis revealed a homozygous pathogenic variant (c.736 T > A; Cys246Ser) in exon 6 in LIPH. In our clinic, we identified three additional cases with the homozygous Cys246Ser variant and one case with compound heterozygous variants in LIPH: Cys246Ser and c.671C > G (Pro224Arg). Consequently, genetic analyses, including genotype–phenotype correlation involving rare LIPH variants, have become more crucial in the Japanese population.

Mitochondrial cardiomyopathy: a puzzle for the final diagnosis.

Hypertrophic cardiomyopathy in children has diverse causes. Mitochondrial diseases, a rare aetiology leading to cardiomyopathy in 20-40% of affected children, predominantly present as hypertrophic cardiomyopathy. Diagnosis is challenging due to inconsistent genotype-phenotype correlation, resulting in various clinical presentations. We present a case of a one-month-old infant with severe hypertrophic cardiomyopathy and cardiac tamponade. Genetic diagnosis revealed a Valyl-tRNA synthetase 2 (VARS2) gene mutation, linking it to mitochondrial encephalopathy-cardiomyopathy. This case highlights novel variants and expands the understanding of hypertrophic cardiomyopathy aetiology in infants.

Characterization of a novel HDAC2 pathogenetic variant: a missing puzzle piece for chromatinopathies.

Histone deacetylases (HDACs) are enzymes pivotal for histone modification (i.e. acetylation marks removal), chromatin accessibility and gene expression regulation. Class I HDACs (including HDAC1, 2, 3, 8) are ubiquitously expressed and they often participate in multi-molecular protein complexes. To date, three neurodevelopmental disorders caused by mutations in genes encoding for HDACs (HDAC4, HDAC6 and HDAC8) and thus belonging to the group of chromatinopathies, have been described. We performed whole exome sequencing (WES) for a patient (#249) clinically diagnosed with the chromatinopathy Rubinstein-Taybi syndrome (RSTS) but negative for mutations in RSTS genes, identifying a de novo frameshift variant in HDAC2 gene. We then investigated its molecular effects in lymphoblastoid cell lines (LCLs) derived from the patient compared to LCLs from healthy donors (HD). As the variant was predicted to be likely pathogenetic and to affect the sequence of nuclear localization signal, we performed immunocytochemistry and lysates fractionation, observing a nuclear mis-localization of HDAC2 compared to HD LCLs. In addition, HDAC2 total protein abundance resulted altered in patient, and we found that newly identified variant in HDAC2 affects also acetylation levels, with significant difference in acetylation pattern among patient #249, HD and RSTS cells and in expression of a known molecular target. Remarkably, RNA-seq performed on #249, HD and RSTS cells shows differentially expressed genes (DEGs) common to #249 and RSTS. Interestingly, our reported patient was clinically diagnosed with RSTS, a chromatinopathy which known causative genes encode for enzymes antagonizing HDACs. These results support the role of HDAC2 as causative gene for chromatinopathies, strengthening the genotype-phenotype correlations in this relevant group of disorders.

Clinical and molecular characteristics of hemophilia A affected individuals and carriers: A 24 years experience from three centers.

Hemophilia A is a rare bleeding disorder with variable expressivity and allelic heterogeneity. Despite the advancement of prenatal diagnostics and molecular studies, the number of studies reviewing the reproductive choices of hemophilia A carriers and affected individuals remains limited. Through this retrospective review, we hope to gain a deeper understanding of hemophilia A-affected individuals' clinical and molecular characteristics, as well as the reproductive choices of the at-risk couples. A total of 122 individuals harboring likely causative F8 gene alterations from 64 apparently unrelated families attending three centers between 3/2000 and 3/2023 were included in this study. Their clinical and molecular findings as well as reproductive choices were gathered in a clinical setting and verified through the electronic medical record database of the public health system. Forty-seven affected males and 75 female heterozygous carriers were included in the analysis. Among 64 apparently unrelated families, 36 distinct pathogenic/likely pathogenic variants were identified, of which 30.6% (11/36) of variants were novel. While the majority of clinical findings and genotype-phenotype correlations appear to be in accordance with existing literature, female carriers who had no fertility intention were significantly more likely to have affected sons than those who had fertility intention (5/19 vs. 4/5; p = 0.047). Through this retrospective review, we summarized the clinical and molecular characteristics of 122 individuals harboring pathogenic/likely pathogenic F8 variants, as well as their fertility intentions and reproductive outcomes. Further studies are required to look into the considerations involved in reproductive decision-making.

Genetic profile of Brazilian patients with LAMA2-related dystrophies.

LAMA2-related dystrophies (LAMA2-RD) constitute a rare neuromuscular disorder with a broad spectrum of phenotypic severity. Our understanding of the genotype-phenotype correlations in this condition remains incomplete, and reliable clinical data for clinical trial readiness is limited. In this retrospective study, we reviewed the genetic data and medical records of 114 LAMA2-RD patients enrolled at seven research centers in Brazil. We identified 58 different pathogenic variants, including 21 novel ones. Six variants were more prevalent and were present in 81.5% of the patients. Notably, the c.1255del, c.2049_2050del, c.3976 C>T, c.5234+1G>A, and c.4739dup variants were found in patients unable to walk and without cortical malformation. In contrast, the c.2461A>C variant was present in patients who could walk unassisted. Among ambulatory patients, missense variants were more prevalent (p < 0.0001). Although no specific hotspot regions existed in the LAMA2, 51% of point mutations were in the LN domain, and 88% of the missense variants were found within this domain. Functional analysis was performed in one intronic variant (c.4960-17C>A) and revealed an out-of-frame transcript, indicating that the variant creates a cryptic splicing site (AG). Our study has shed light on crucial phenotype-genotype correlations and provided valuable insights, particularly regarding the Latin American population.

Updates on clinical and laboratory aspects of hereditary dyserythropoietic anemias.

Hereditary dyserythropoietic anemias, or congenital dyserythropoietic anemias (CDAs), are rare disorders disrupting normal erythroid lineage development, resulting in ineffective erythropoiesis and monolinear cytopenia. CDAs include three main types (I, II, III), transcription-factor-related forms, and syndromic forms. The widespread use of next-generation sequencing in the last decade has unveiled novel causative genes and unexpected genotype-phenotype correlations. The discovery of the genetic defects underlying the CDAs not only facilitates accurate diagnosis but also enhances understanding of CDA pathophysiology. Notable advancements include identifying a hepatic-specific role of the SEC23B loss-of-function in iron metabolism dysregulation in CDA II, deepening CDIN1 dysfunction during erythroid differentiation, and uncovering a recessive CDA III form associated with RACGAP1 variants. Current treatments primarily rely on supportive measures tailored to disease severity and clinical features. Comparative studies with pyruvate kinase deficiency have illuminated new therapeutic avenues by elucidating iron dyshomeostasis and dyserythropoiesis mechanisms. We herein discuss recent progress in diagnostic methodologies, novel gene discoveries, and enhanced comprehension of CDA pathogenesis and molecular genetics.

The neuronal ceroid lipofuscinosis type 2 – associated variants: An analysis of alterations in the TPP1 gene and genotype–phenotype correlation in Ukraine

The neuronal ceroid lipofuscinosis type 2 – associated variants: An analysis of alterations in the <i>TPP1</i> gene and genotype–phenotype correlation in Ukraine

Distribution of pathogenic variants in the CFTR gene in a representative cohort of people with cystic fibrosis in the Kingdom of Bahrain

BackgroundCystic fibrosis (CF) is a rare multi-systemic recessive disorder. The spectrum and the frequencies of CFTR mutations causing CF vary amongst different populations in Europe and the Middle East. In this study, we characterised the distribution of CF-causing mutations (i.e. pathogenic variants in the CFTR gene) in a representative CF cohort from the Kingdom of Bahrain based on a three-decade-long analysis at a single tertiary centre. We aim to improve CF genetic diagnostics, introduce of CF neonatal screening and provide CFTR modulator therapy (CFTRm).MethodsCFTR genotyping and associated clinical information were drawn from a longitudinal cohort. We sequenced 56 people with CF (pwCF) that had one or both CFTR mutations unidentified and carried out comprehensive bioinformatic- and family-based segregation analyses of detected variants, including genotype–phenotype correlations and disease incidence estimates. The study methodology could serve as a basis for other non-European CF populations with a high degree of consanguinity.ResultsAltogether 18 CF-causing mutations were identified, 15 of which were not previously detected in Bahrain, accounting for close to 100% of all population-specific alleles. The most common alleles comprise c.1911delG [2043delG; 22.8%], c.2988+1G > A [3120+1G>A; 16.3%], c.2989-1G>A [3121-1G>A; 14.1%], c.3909C>G [N1303K; 13.0%], and c.1521_1523delCTT [p.PheF508del; 7.6%]. Although the proportion of 1st cousin marriages has decreased to 50%, the frequency of homozygosity in our pwCF is 67.4%, thereby indicating that CF still occurs in large, often related, families. pwCF in Bahrain present with faltering growth, pancreatic insufficiency and classical sino-pulmonary manifestations. Interestingly, two pwCF also suffer from sickle cell disease. The estimated incidence of CF in Bahrain based on data from the last three decades is 1 in 9,880 live births.ConclusionThe most commonCF-causing mutations in Bahraini pwCF were identified, enabling more precise diagnosis, introduction of two-tier neonatal screening and fostering administration of CFTRm.

Epidermolytic ichthyosis: Clinical spectrum and burden of disease in a large German cohort.

Keratinopathic ichthyoses are a group of hereditary skin disorders caused by pathogenic variants in keratin genes such as KRT1, KRT2 and KRT10, resulting in conditions such as epidermolytic ichthyosis (EI), autosomal-recessive EI, superficial EI and epidermal nevus. Case reports highlight the diversity of clinical manifestations, but only limited information exists regarding the quality of life and burden of disease. The objective of this study was to assess the clinical spectrum, genotype-phenotype correlations and burden of disease in patients with epidermolytic ichthyosis in Germany. We conducted an observational study involving 48 patients diagnosed with EI. Evaluations included the severity of skin involvement using the Investigator's Global Assessment (IGA), the modified Ichthyosis Area Severity Index (mIASI) and complications. The burden of disease was evaluated using the Dermatology Life Quality Index (DLQI) or the Children's Dermatology Life Quality Index (cDLQI). Based on clinical features, mIASI and IGA, EI can be categorized into localized, intermediate and severe forms. Patients with keratin 1 mutations tended to have severe EI, while the three forms were evenly distributed in those with keratin 10 mutations. The study highlights that around half of the patients with EI experienced itch and severe pain. Quality of life was affected, with daily life restrictions of 78% due to care and therapies. Reimbursement for moisturizing ointments by health insurance was insufficient for one-quarter of cases. The results emphasize the need for targeted interventions and comprehensive care strategies to enhance the quality of life for affected individuals.

Neuropsychological profile associated with KAT6A syndrome: Emergent genotype-phenotype trends

BackgroundKAT6A (Arboleda-Tham) syndrome is a Mendelian disorder of the epigenetic machinery caused by pathogenic variants in the lysine acetyltransferase 6 A (KAT6A) gene. Intellectual disability and speech/language impairment (e.g., minimally verbal) are common features of the disorder, with late-truncating variants associated with a more severe form of intellectual disability. However, much of the cognitive phenotype remains elusive given the dearth of research.Participants and methodsThis study examined non-verbal and social skills of 15 individuals with molecularly-confirmed diagnoses of KAT6A syndrome (Mean age = 10.32 years, SD = 4.12). Participants completed select subtests from the DAS-II, the NEPSY-II, and the Beery Buktenica Developmental Test of Visual Motor Integration 6th Edition, and their caregivers completed an assortment of behavior rating inventories.ResultsFindings suggest global cognitive impairment with nonverbal cognition scores similar to those for receptive language. Autism-related features, particularly restricted interests and repetitive behaviors, and broad adaptive deficits were common in our sample juxtaposed with a relatively strong social drive and low frequency of internalizing and externalizing behavioral problems. A general trend of lower performance scores on nonverbal and receptive language measures was observed among those with protein-truncating variants vs. missense variants; however, no effect was observed on caregiver rating inventories of daily behaviors. Late and early truncating variants yielded comparable neuropsychological profiles.ConclusionsOverall, study results show the cognitive phenotype of KAT6A syndrome includes equally impaired nonverbal cognition and receptive language functioning, paired with relatively intact social drive and strengths in behavior regulation. Emergent genotype-phenotype correlations suggest cognition may be more affected in protein-truncating than missense mutations although similar neurobehavioral profiles were observed.

Genotype-phenotype severity correlation in a multicentric portuguese cohort of ABCA4-associated retinopathy

PurposeTo investigate genotype-phenotype correlations in ABCA4-associated retinopathy and further validate a recently proposed genotype-phenotype correlation model. DesignMulticentric, cross-sectional cohort study. MethodsConsecutive patients with genetically confirmed ABCA4-associated retinopathy from three Portuguese centres were included. Patients were categorized into distinct phenotype groups according to the degree of hypoautofluorescence and retinal background appearance in ultra-widefield fundus autofluorescence (UW-FAF) imaging. Genotype classification was performed using two criteria: one according to the presence of the p.Gly1961Glu variant, a hypomorphic variant, at least one moderate variant, or two biallelic severe/PVS1 variants (genotype classification A, which corresponds to the newly described criteria); and another one based on the number of null variants identified (genotype classification B). Associations between clinical data and phenotype and genotype groups were analysed. ResultsA total of 50 patients were included. Significant correlations between age of onset, best-corrected visual acuity (BCVA), and both phenotype and genotype groups were found, with patients in more severe phenotype and genotype categories exhibiting earlier disease onset and poorer visual function (p < 0.001; p < 0.001; p < 0.001; p < 0.001, p < 0.001; and p = 0.004, respectively). Genotype classification A better predicted phenotype severity on UW-AF imaging, demonstrating milder genotypes in patients with less severe phenotypes and more severe genotypes in those with advanced disease (p < 0.001). A genotype-phenotype correlation matrix was constructed based on the classification of the two disease-causing variants and their corresponding phenotypic staging. ConclusionOur findings support the utility of the newly described genotype classification in evaluating ABCA4-associated retinopathy phenotype severity, with possible implications in future understanding of the disease genetics and assessment of individual prognosis for patients.

Genetic analysis of a child with Multiple congenital anomalies-hypotonia-seizures syndrome 1 due to variant of PIGN gene

To analyze the clinical phenotype and genetic etiology of a child with Multiple congenital anomalies-hypotonia-seizures syndrome 1 (MCAHS1). Clinical data of a 2-year-old boy who had presented at the Affiliated Hospital of Qingdao University in March 2023 for "intermittent limb twitching for 2 years" was collected. Peripheral blood samples were collected from the child and his parents for whole-exome sequencing (WES). Candidate variants were verified by Sanger sequencing and bioinformatic analysis based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The child had manifested with distinctive facial features, limb deformities, hypotonia, motor and intellectual delays, and epileptic seizures. WES revealed that he has harbored compound heterozygous variants of the PIGN gene, namely c.963G>A (p.Q321=) and c.994A>T (p.I332F), which were inherited from his phenotypically normal mother and father, respectively. Based on the ACMG guidelines, the c.963G>A was classified as a pathogenic variant (PVS1+PM2_Supporting+PM3), whilst the c.994A>T was classified as a variant of uncertain significance (PM2_Supporting+PP3). Above discovery has expanded the mutational spectrum of the PIGN gene variants associated with MCAHS1, which may facilitate delineation of its genotype-phenotype correlation.

IKAROS—how many feathers have you lost: mild and severe phenotypes in IKZF1 deficiency

Heterozygous germline variants in human IKZF1 encoding for IKAROS define an inborn error of immunity with immunodeficiency, immune dysregulation and risk of malignancy with a broad phenotypic spectrum. Growing evidence of underlying pathophysiological genotype-phenotype correlations helps to improve our understanding of IKAROS-associated diseases. We describe 6 patients from 4 kindreds with two novel IKZF1 variants leading to haploinsufficiency from 3 centers in Germany. We also provide an overview of first symptoms to a final diagnosis including data from the literature.

Comprehensive analyses of phenylalanine hydroxylase variants and phenotypic characteristics of patients in the eastern region of Türkiye.

Phenylalanine hydroxylase (PAH) is predominantly a hepatic enzyme that catalyzes phenylalanine (Phe) into tyrosine, which is the rate-limiting step in Phe catabolism. Biallelic variants in the PAH gene cause PAH enzyme deficiency. Phenylketonuria (PKU) is an autosomal recessive disorder that causes neurologic, behavioral, and dermatological findings. PKU could be divided clinically into three types based on the blood Phe levels: classic phenylketonuria (cPKU), mild-moderate phenylketonuria (mPKU), and mild hyperphenylalaninemia (MHP). This study aimed to determine the phenotypic and genotypic characteristics of Turkish PKU patients in the eastern region of Türkiye. Demographic characteristics, serum Phe levels, treatments, and PAH variants of 163 patients with PKU and hyperphenylalaninemia (HPA) were retrospectively evaluated. Blood Phe levels of the patients were analyzed with the high-performance liquid chromatography method. For PAH gene analysis, next-generation sequencing was performed. Of the 163 patients included in the study, 38 (23.3 %) had cPKU, 16 (9.8 %) had mPKU, and 109 (66.9 %) had MHP. Homozygous variants in the PAH gene were detected in 66 (40.5 %) of the patients, while compound heterozygous variants were detected in 97 (59.5 %) patients. Two novel and 35 recurrent variants in the PAH gene were detected. Of the twonovel variants, one was missense (p.Phe351Leu) and the other was frameshift (p.Met276Cysfs*65). The most frequently detected variants were p.Thr380Met (18 %), p.Arg261Gln (16.8 %), and p.Ala300Ser (12.8 %). All patients with the homozygous c.1066-11G>A variant exhibited cPKU phenotype. The c.898G>T (p.Ala300Ser), c.1139C>T (p.Thr380Met), and c.1208C>T (p.Ala403Val) variants were statistically related to mild phenotype. On the other hand, c.592_613del (p.Tyr198Serfs*136), c.1028A>G (p.Tyr343Cys), and c.782G>A (p.Arg261Gln) variants were more frequently detected in the cPKU group. Our study, conducted with patients from the eastern region of Türkiye, demonstrates the genetic heterogeneity in the Turkish population. Simultaneously, our research contributes to genotype-phenotype correlation and expands the genotypic spectrum by identifying novel variants.

Genotypic and phenotypic characterization of a cohort of patients affected by rod CNG channel-associated retinitis pigmentosa.

Retinitis pigmentosa (RP), a heterogeneous inherited retinal disorder causing gradual vision loss, affects over 1 million people worldwide. Pathogenic variants in CNGA1 and CNGB1 genes, respectively accounting for 1% and 4% of cases, impact the cyclic nucleotide-gated channel in rod photoreceptor cells. The aim of this study is to describe and compare genotypic and clinical characteristics of a cohort of patients with CNGA1- or CNGB1-related RP and to explore potential genotype-phenotype correlations. The following data from patients with CNGA1- or CNGB1-related RP, followed in five Italian inherited retinal degenerations services, were retrospectively collected: genetic variants in CNGA1 and CNGB1, best-corrected visual acuity (BCVA), ellipsoid zone (EZ) width, fundus photographs and short-wavelength fundus autofluorescence (SW-AF) images. Comparisons and correlation analyses were performed by first dividing the cohort in two groups according to the gene responsible for the disease (CNGA1 and CNGB1 groups). In parallel, the whole cohort of RP patients was divided into two other groups, according to the expected impact of the variants at protein level (Low and High group). In total, 29 patients were recruited, 11 with CNGA1- and 18 with CNGB1-related RP. In both CNGA1 and CNGB1, 5 novel variants in CNGA1 and 5 in CNGB1 were found. BCVA was comparable between CNGA1 and CNGB1 groups, as well as between Low and High groups. CNGA1 group had a larger mean EZ width compared to CNGB1 group, albeit not statistically significant, while EZ width did not differ between Low and High groups A statistically significant correlation between EZ width and BCVA as well as between EZ width and age were observed in the whole cohort of RP patients. Fundus photographs of all patients in the cohort showed classic RP pattern, and in SW-AF images an hyperautofluorescent ring was observed in 14/21 patients. Rod CNG channel-associated RP was demonstrated to be a slowly progressive disease in both CNGA1- and CNGB1-related forms, making it an ideal candidate for gene augmentation therapies.

Hypogonadotropic hypogonadism, phenotype genotype correlation

Hypogonadotropic hypogonadism, phenotype genotype correlation