The Study of the Inheritance Mechanisms of Myotonic Dystrophy Type 1 (DM1) in Families from the Republic of North Ossetia-Alania.

Myotonic dystrophy type 1 (DM1) is a multisystem disorder with progressive myopathy and myotonia. The clinical study was conducted in the Republic of North Ossetia-Alania (RNOA), and in it 39 individuals from 17 unrelated families were identified with DM1. Clinical presentations varied, including muscle weakness, fatigue, intellectual disability, hypersomnia, ophthalmological abnormalities, and alopecia. Using clinical and genotyping data, we confirmed the diagnosis and enabled the study of CTG-repeat anticipation and DM1 prevalence in the Ossetian and Ingush populations. CTG expansion correlated with age of onset, with clinical severity, and with offspring showing more severe symptoms than parents. In many families, the youngest child had a more severe DM1 phenotype than older siblings. The prevalence was 14.17 per 100,000 in Ossetians and 18.74 per 100,000 in Ingush people, aligning with global data. Segregation analysis showed a higher frequency of maternal transmission. The study highlights the clinical and genetic heterogeneity of DM1 and its dependence on repeat expansion and paternal and maternal age.

Cases report: Mosaic structural variants of the EXT1 gene in previously genetically unconfirmed multiple osteochondromas.

Multiple osteochondromas (MO) is a rare autosomal dominant skeletal disorder characterized by the development of multiple benign tumors known as osteochondromas. The condition is predominantly caused by loss-of-function variants in the EXT1 or EXT2 genes, facilitating relatively precise clinical diagnosis through established diagnostic criteria. Despite this, a notable percentage of MO cases (10%-20%) remains unresolved after sequencing coding regions and copy number analysis of both genes. In our study, we identified mosaic structural variants in two patients who initially yielded negative results on standard genetic analysis for MO. Specifically, mosaic deletions affecting exons 8-11 and exons 2-11 in the EXT1 gene were detected. RNA analysis was performed in one case, while both cases underwent genome sequencing. To date, only six mosaic copy number variations have been reported in association with MO, representing a minority among known variants in both genes. Our report provides a detailed analysis of these findings, highlighting the significance of advanced genetic testing techniques in detecting mosaic variants in the EXT1/2 genes.

Asymmetric scapuloperoneal phenotype of MATR3-related distal myopathy: case series.

Recent research has sparked a discussion on the spectrum of diseases linked to the MATR3 gene associated with amyotrophic lateral sclerosis and distal myopathy with vocal cord and pharyngeal weakness (VCPDM). To date, fewer than 50 cases of VCPDM have been reported in the literature. We aim to build upon the work of previous researchers by gathering additional information about VCPDM. In this study, we present six patients from four unrelated families affected by VCPDM. Our observations include patients exhibiting both the typical phenotype associated with MATR3-related distal myopathy and rare symptomatic manifestations of the disease. Notably, two cases presented with an asymmetric scapuloperoneal phenotype, leading in one case to an initial misdiagnosis of facioscapulohumeral muscular dystrophy.

Rare Variants of the SMN1 Gene Detected during Neonatal Screening.

During the expanded neonatal screening program conducted in 2023, we analyzed samples obtained from 1,227,130 out of 1,256,187 newborns in the Russian Federation in order to detect 5q spinal muscular atrophy (5q SMA). Within the 253-sample risk group formed based on the results of the first screening stage, 5 samples showed a discrepancy between the examination results obtained via various screening methods and quantitative MLPA (used as reference). The discrepancy between the results was caused by the presence of either a c.835-18C>T intronic variant or a c.842G>C p.(Arg281Thr) missense variant in the SMN1 gene, both of which are located in the region complementary to the sequences of annealing probes for ligation and real-time PCR. Three newborns had the c.835-18C>T variant in a compound heterozygous state with a deletion of exons 7-8 of the SMN1 gene, one newborn with two copies of the SMN1 gene had the same variant in a heterozygous state, and one newborn had both variants-c.835-18C>T and c.842G>C p.(Arg281Thr)-in a compound heterozygous state. Additional examination was carried out for these variants, involving segregation analysis in families, carriage analysis in population cohorts, and RNA analysis. Based on the obtained results, according to the ACMG criteria, the c.835-18C>T intronic variant should be classified as likely benign, and the c.842G>C p.(Arg281Thr) missense substitution as a variant of uncertain clinical significance. All five probands are under dynamic monitoring. No 5q SMA symptoms were detected in these newborns neonatally or during a 1-year follow-up period.

Genetic Landscape of SH3TC2 variants in Russian patients with Charcot-Marie-Tooth disease.

Introduction: Charcot-Marie-Tooth disease type 4C (CMT4C) OMIM#601596 stands out as one of the most prevalent forms of recessive motor sensory neuropathy worldwide. This disorder results from biallelic pathogenic variants in the SH3TC2 gene. Methods: Within a cohort comprising 700 unrelated Russian patients diagnosed with Charcot-Marie-Tooth disease, we conducted a gene panel analysis encompassing 21 genes associated with hereditary neuropathies. Among the cohort, 394 individuals exhibited demyelinating motor and sensory neuropathy. Results and discussion: Notably, 10 cases of CMT4C were identified within this cohort. The prevalence of CMT4C among Russian demyelinating CMT patients lacking the PMP22 duplication is estimated at 2.5%, significantly differing from observations in European populations. In total, 4 novel and 9 previously reported variants in the SH3TC2 gene were identified. No accumulation of a major variant was detected. Three previously reported variants, c.2860C>T p. (Arg954*), p. (Arg658Cys) and c.279G>A p. (Lys93Lys), recurrently detected in unrelated families. Nucleotide alteration p. (Arg954*) is present in most of our patients (30%).

Presentation of Rare Phenotypes Associated with the FKBP10 Gene.

Pathogenic variants in the FKBP10 gene lead to a spectrum of rare autosomal recessive phenotypes, including osteogenesis imperfecta (OI) Type XI, Bruck syndrome Type I (BS I), and the congenital arthrogryposis-like phenotype (AG), each with variable clinical manifestations that are crucial for diagnosis. This study analyzed the clinical-genetic characteristics of patients with these conditions, focusing on both known and newly identified FKBP10 variants. We examined data from 15 patients, presenting symptoms of OI and joint contractures. Diagnostic methods included genealogical analysis, clinical assessments, radiography, whole exome sequencing, and direct automated Sanger sequencing. We diagnosed 15 patients with phenotypes due to biallelic FKBP10 variants-4 with OI Type XI, 10 with BS I, and 1 with the AG-like phenotype-demonstrating polymorphism in disease severity. Ten pathogenic FKBP10 variants were identified, including three novel ones, c.1373C>T (p.Pro458Leu), c.21del (p.Pro7fs), and c.831_832insCG (p.Gly278Argfs), and a recurrent variant, c.831dup (p.Gly278Argfs). Variant c.1490G>A (p.Trp497Ter) was found in two unrelated patients, causing OI XI in one and BS I in the other. Additionally, two unrelated patients with BS I and epidermolysis bullosa shared identical homozygous FKBP10 and KRT14 variants. This observation illustrates the diversity of FKBP10-related pathology and the importance of considering the full spectrum of phenotypes in clinical diagnostics.

Genetic Landscape and Clinical Features of Hyperphenylalaninemia in North Ossetia-Alania: High Frequency of P281L and P211T Genetic Variants in the PAH Gene.

This study, conducted in the Republic of North Ossetia-Alania (RNOA), aimed to explore the genetic landscape of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) in the Ossetian population using data from newborn screening (NBS). Through comprehensive molecular genetic analysis of 29 patients with HPA from diverse ethnic backgrounds, two major genetic variants in the PAH gene, P281L and P211T, were identified, constituting 50% of all detected pathogenic alleles in Ossetian patients. Remarkably, these variants exhibited an exceptionally high frequency in the Ossetian population, surpassing global prevalence rates. This study unveiled a notable prevalence of mild forms of HPA (78%), underscoring the importance of genetic counseling for carriers of pathogenic variants in the PAH gene. Moreover, the findings emphasized the necessity for ongoing monitoring of patients with mild forms, as they may lack significant symptoms for diagnosis, potentially impacting offspring. Overall, this research offers valuable insights into the genetic landscape of HPA and PKU in the Ossetian population.

Epidemiology of Spinal Muscular Atrophy Based on the Results of a Large-Scale Pilot Project on 202,908 Newborns.

BACKGROUND: This study presents the findings of a newborn screening (NBS) pilot project for 5q-spinal muscular atrophy (5q-SMA) in multiple regions across Russia for during the year 2022. The aim was to assess the feasibility and reproducibility of NBS for SMA5q in diverse populations and estimate the real prevalence of 5q-SMA in Russia as well as the distribution of patients with different number of SMN2 copies. METHODS: The pilot project of NBS here was based on data, involving the analysis of 202,908 newborns. SMA screening assay was performed using a commercially available real-time polymerase chain reaction kit, the Eonis SCID-SMA. RESULTS: In one year, 202,908 newborns were screened, identifying 26 infants with homozygous deletion of SMN1 exon 7, yielding an estimated 5q-SMA incidence of 1:7804 newborns. It was found that 38.46% had two SMN2 copies, 42.31% had three copies, 15.38% had four copies, and 3.85% had five copies of SMN2. Immediate treatment was proposed for patients with two or three SMN2 copies. Infants with four or more SMN2 copies warranted further investigation on management and treatment. Short-term monitoring after gene therapy showed motor function improvements. Delays in treatment initiation were observed, including the testing for adeno-associated virus 9 antibodies and nonmedical factors. CONCLUSIONS: The study emphasizes the need for a standardized algorithm for early diagnosis and management through NBS to benefit affected families. Overall, the NBS program for 5q-SMA in Russia demonstrated the potential to improve outcomes and transform SMA from a devastating disease to a chronic condition with evolving medical requirements.

Newborn Screening for Severe T and B Cell Lymphopenia Using TREC/KREC Detection: A Large-Scale Pilot Study of 202,908 Newborns.

Newborn screening (NBS) for severe inborn errors of immunity (IEI), affecting T lymphocytes, and implementing measurements of T cell receptor excision circles (TREC) has been shown to be effective in early diagnosis and improved prognosis of patients with these genetic disorders. Few studies conducted on smaller groups of newborns report results of NBS that also include measurement of kappa-deleting recombination excision circles (KREC) for IEI affecting B lymphocytes. A pilot NBS study utilizing TREC/KREC detection was conducted on 202,908 infants born in 8 regions of Russia over a 14-month period. One hundred thirty-four newborns (0.66‰) were NBS positive after the first test and subsequent retest, 41% of whom were born preterm. After lymphocyte subsets were assessed via flow cytometry, samples of 18 infants (0.09‰) were sent for whole exome sequencing. Confirmed genetic defects were consistent with autosomal recessive agammaglobulinemia in 1/18, severe combined immunodeficiency - in 7/18, 22q11.2DS syndrome - in 4/18, combined immunodeficiency - in 1/18 and trisomy 21 syndrome - in 1/18. Two patients in whom no genetic defect was found met criteria of (severe) combined immunodeficiency with syndromic features. Three patients appeared to have transient lymphopenia. Our findings demonstrate the value of implementing combined TREC/KREC NBS screening and inform the development of policies and guidelines for its integration into routine newborn screening programs.

Generation of induced pluripotent stem cell line (RCMGi012-A) from fibroblasts of patient with mucopolysaccharidosis type VI.

Skin fibroblasts obtained from a 5-year-old girl with genetically proven (two heterozygous mutations in ARSB gene) and clinically manifested mucopolysaccharidosis type VI were successfully transformed into induced pluripotent stem cells by using Sendai virus-based reprogramming vectors including the four Yamanaka factors namely SOX2, OCT3/4, KLF4, and c-MYC. These iPSCs expressed pluripotency markers, had a normal karyotype and the potential to differentiate into three germ layers in spontaneous differentiation assay. The line may be used for cell differentiation and pharmacological investigations, and also may provide a model for development of a personalized treatment including drug screening and genome editing.

A Molecular Genetic Analysis of RPE65-Associated Forms of Inherited Retinal Degenerations in the Russian Federation.

Pathogenic variants in the RPE65 gene cause the only known form of inherited retinal degenerations (IRDs) that are prone to gene therapy. The current study is aimed at the evaluation of the prevalence of RPE65-associated retinopathy in the Russian Federation, the characterization of known variants in the RPE65 gene, and the establishment of the specificities of the mutation spectrum in Russian patients. METHODS: The analysis was carried out on blood samples obtained from 1053 non-related IRDs patients. The analysis, which consisted of 211 genes, was carried out based on the method of massive parallel sequencing (MPS) for all probands. Variant validation, as well as biallelic status verification, were carried out using direct automated Sanger sequencing. The number of copies of RPE65 exons 1-14 was analyzed with quantitative MLPA using an MRC-Holland SALSA MLPA probemix. RESULTS: Out of 1053 non-related patients, a molecular genetic diagnosis of IRDs has been confirmed in 474 cases, including 25 (5.3%) patients with RPE65-associated retinopathy. We detected 26 variants in the RPE65 gene, nine of which have not been previously described in the literature. The most common mutations in the Russian population were c.304G>T/p.(Glu102*), c.370C>T/p.(Arg124*), and c.272G>A/p.(Arg91Gln), which comprised 41.8% of all affected chromosomes. CONCLUSIONS: The current study shows that pathogenic variants in the RPE65 gene contribute significantly to the pathogenesis of IRDs and comprise 5.3% of all patients with a confirmed molecular genetic diagnosis. This study allowed for the formation of a cohort for target therapy of the disorder; such therapy has already been carried out for some patients.

Pathogenic Variants and Genotypes of the CFTR Gene in Russian Men with Cystic Fibrosis and CBAVD Syndrome.

Pathogenic CFTR variants cause cystic fibrosis (CF), and CF-related disorders (CF-RD), including bilateral aplasia of the vas deferens (CBAVD). The spectrum of clinical manifestations depends on the CFTR genotype. The frequency and spectrum of the CFTR variants vary between populations and clinical groups. CFTR variants and genotypes were analyzed in Russian men with CF (n = 546) and CBAVD syndrome (n = 125). Pathogenic variants were detected in 93.95% and 39.2% of the CF and CBAVD alleles, respectively. The most frequent c.1521_1523del (F508del; p.Phe508del) variant was found in 541 (49.5%) CF alleles. A total of 162 CFTR genotypes were revealed in CF patients, including 152 homozygous and 394 compound-heterozygous. The most common CF-genotype was F508del/F508del (24.9%). Other frequent CF-genotypes were F508del/3849+10kbC>T, F508del/CFTRdele2,3, and F508del/E92K. CF-causing variants and/or 5T allele were found in 88% of CBAVD patients: 5T/CFTRmut (48.0%), CFTRmut/N (17.6%), CFTRmut/CFTRmut (6.4%), 5T/5T (10.4%), 5T/N (5.6%) and N/N (12.0%), with the most common CBAVD-genotype being F508del/5T (29.6%). The allele frequencies of F508del, CFTRdele2,3 394delTT, and 3849+10kbC>T were significantly higher in CF patients. L138ins/L138ins, 2184insA/E92K, and L138ins/N genotypes were found in CBAVD, but not in CF patients. The results indicate certain differences in the frequency of some CFTR variants and genotypes in Russian CF and CBAVD patients.

Step-by-Step Double-Trouble OBAIRH and DMD Diagnosis in a One-Year-Old Boy.

We present a case of a combination of two rare hereditary disorders: obesity, adrenal insufficiency and red hair syndrome (OBAIRH) and Duchenne muscular dystrophy (DMD) in a boy. Both diseases were diagnosed during the first year of life. OBAIRH was suggested based on the ethnicity and family history of the patient, while DMD was based on an extreme increase in transaminase and CK (creatine kinase) levels during a biochemical analysis of his blood. The OBAIRH syndrome was caused by a pathogenic homozygous variant in the regulatory region of the POMC gene (NM_001035256.3): c.-71+1G>A, while DMD was caused by the de novo deletion of exons 38-45 of the DMD (NM_004006.3) gene (NC_000023.10:g.(?_32380941)(31950285_?)del).

GABRA1-Related Disorders: From Genetic to Functional Pathways.

OBJECTIVE: Variants in GABRA1 have been associated with a broad epilepsy spectrum, ranging from genetic generalized epilepsies to developmental and epileptic encephalopathies. However, our understanding of what determines the phenotype severity and best treatment options remains inadequate. We therefore aimed to analyze the electroclinical features and the functional effects of GABRA1 variants to establish genotype-phenotype correlations. METHODS: Genetic and electroclinical data of 27 individuals (22 unrelated and 2 families) harboring 20 different GABRA1 variants were collected and accompanied by functional analysis of 19 variants. RESULTS: Individuals in this cohort could be assigned into different clinical subgroups based on the functional effect of their variant and its structural position within the GABRA1 subunit. A homogenous phenotype with mild cognitive impairment and infantile onset epilepsy (focal seizures, fever sensitivity, and electroencephalographic posterior epileptiform discharges) was described for variants in the extracellular domain and the small transmembrane loops. These variants displayed loss-of-function (LoF) effects, and the patients generally had a favorable outcome. A more severe phenotype was associated with variants in the pore-forming transmembrane helices. These variants displayed either gain-of-function (GoF) or LoF effects. GoF variants were associated with severe early onset neurodevelopmental disorders, including early infantile developmental and epileptic encephalopathy. INTERPRETATION: Our data expand the genetic and phenotypic spectrum of GABRA1 epilepsies and permit delineation of specific subphenotypes for LoF and GoF variants, through the heterogeneity of phenotypes and variants. Generally, variants in the transmembrane helices cause more severe phenotypes, in particular GoF variants. These findings establish the basis for a better understanding of the pathomechanism and a precision medicine approach in GABRA1-related disorders. Further studies in larger populations are needed to provide a conclusive genotype-phenotype correlation. ANN NEUROL 2023.

L138ins Variant of the CFTR Gene in Russian Infertile Men.

(1) Introduction: Pathogenic variants in the CFTR (Cystic Fibrosis Transmembrane conductance Regulator, OMIM: 602421) gene cause Cystic Fibrosis (CF, OMIM: 219700) and CF-related disorders (CF-RD), often accompanied by obstructive azoospermia due to congenital bilateral aplasia of vas deferens (CBAVD, OMIM: 277180) in male patients. The L138ins (c.413_415dup; p. (Leu138dup)) is a mild variant in the CFTR gene that is relatively common among CF-patients in Slavic populations. The frequency of this variant in Russian infertile men has not been sufficiently studied; (2) Materials and Methods: The sample consisted of 6033 Russian infertile men. The patients were tested for 22 common in Russian populations pathogenic variants of the CFTR gene and the IVS9Tn-polymorphic locus of the intron 9. Molecular-genetic studies were performed using amplified fragment length polymorphism (AFLP-PCR), multiplex ligation-dependent probe amplification (MLPA), and nested PCR (for analysis of the IVS9Tn-polymorphic locus); (3) Results: Pathogenic variants in the CFTR were detected in 3.9% of patients. The most frequent variants were F508del and CFTRdele2.3(21kb), accounted for 61.0% and 7.1% of detected variants, respectively. The L138ins variant was detected in 17 (0.28%) individuals: one of them was homozygous, 10 patients were heterozygous, and 6 patients were compound-heterozygous (F508del/L138ins, n = 4; L138ins/N1303K, n = 1; L138ins/5T, n = 1). Two pathogenic CF-causing variants in the CFTR gene were detected in 8 patients, including 7 compound heterozygous (F508del/L138ins, n = 4; F508del/N1303K, n = 1; 2184insA/E92K, n = 1; 3849+10kbC>T/E92K, n = 1) and one homozygous (L138ins/L138ins). The L138ins variant was found in 7 out of 16 (43.75%) chromosomes in six of these patients. The most common pathogenic variant, F508del, was identified in five out of them, in 5 of 16 (31.25%) chromosomes. The allele frequency (AF) of the L138ins variant in the sample has been found to be 0.0014.; (4) Conclusions: The L138ins variant of the CFTR gene is the third most common variant after F508del and CFTRdele2.3(kb) among Russian infertile men.

Evaluation of Pathogenicity and Causativity of Variants in the MPZ and SH3TC2 Genes in a Family Case of Hereditary Peripheral Neuropathy.

The implementation of NGS methods into clinical practice allowed researchers effectively to establish the molecular cause of a disorder in cases of a genetically heterogeneous pathology. In cases of several potentially causative variants, we need additional analysis that can help in choosing a proper causative variant. In the current study, we described a family case of hereditary motor and sensory neuropathy (HMSN) type 1 (Charcot-Marie-Tooth disease). DNA analysis revealed two variants in the SH3TC2 gene (c.279G>A and c.1177+5G>A), as well as a previously described variant c.449-9C>T in the MPZ gene, in a heterozygous state. This family segregation study was incomplete because of the proband's father's unavailability. To evaluate the variants' pathogenicity, minigene splicing assay was carried out. This study showed no effect of the MPZ variant on splicing, but the c.1177+5G>A variant in the SH3TC2 gene leads to the retention of 122 nucleotides from intron 10 in the RNA sequence, causing a frameshift and an occurrence of a premature stop codon (NP_078853.2:p.Ala393GlyfsTer2).

Clinical and Genetic Characteristics of Calvarial Doughnut Lesions with Bone Fragility in Three Families with a Reccurent SGMS2 Gene Variant.

Calvarial doughnut lesions (CDL) with bone fragility with or without spondylometaphyseal dysplasia (MIM: #126550) is a rare autosomal dominant skeletal disorder characterized by low bone mineral density, spinal and peripheral fractures, and specific sclerotic lesions of the cranial bones. In the current classification of skeletal disorders, the disease is included in the group of bone fragility disorders along with osteogenesis imperfecta. The disease is caused by pathogenic variants in the SGMS2 gene, the protein product of which is sphingomyelin synthase 2, which primarily contributes to sphingomyelin (SM) synthesis-the main lipid component of the plasma membrane essential for bone mineralization. To date, 15 patients from eight families with CDL with bone fragility have been described in the literature, and a recurrent variant c.148C>T (p.Arg50Ter) in the SGMS2 gene has been identified, which was found in patients from six families. We diagnosed the disease in 11 more patients from three unrelated families, caused by the same heterozygous nonsense variant c.148C>T (p.Arg50Ter) in the SGMS2 gene. Our results show wide interfamilial and intrafamilial phenotypic variability in patients with a detected recurrent variant in the SGMS2 gene, the presence of which must be taken into consideration in the diagnosis of the disease. The primary analysis of this variant will contribute to optimal molecular genetic diagnostics, which can reduce diagnostic costs and time.

Pilot Program of Newborn Screening for 5q Spinal Muscular Atrophy in the Russian Federation.

5q spinal muscular atrophy (5q SMA) is one of the most common autosomal recessive disorders in the Russian Federation. The first medication to treat 5q SMA was registered in the Russian Federation for treatment of all 5q SMA types in 2019, and the last of the three currently available in December 2021. We launched the pilot newborn screening (NBS) program for 5q SMA in Moscow, the Russian Federation, starting in 2019. During the pilot program, 23,405 neonates were tested for the deletion of exon 7 of the SMN1 gene, the most common cause of 5q SMA. We used the SALSA® MC002 SMA Newborn Screen Kit (MRC Holland) to specifically detect homozygous deletions of SMN1 exon 7. We used the restriction fragment length polymorphism (RFLP) approach to validate detected homozygous deletions and the SALSA MLPA Probemix P060 SMA Carrier Kit (MRC Holland) to determine the SMN2 exon 7 copy number to prescribe gene therapy for 5q SMA. Three newborns with a homozygous deletion of the SMN1 gene were detected. The calculated birth prevalence of 1:7801 appears to be similar to the results in other European countries. The children did not show any signs of respiratory involvement or bulbar weakness immediately after birth. Until now, no 5q SMA case missed by NBS has been detected.

Clinical Presentation of a Patient with a Congenital Disorder of Glycosylation, Type IIs (ATP6AP1), and Liver Transplantation.

The congenital disorder of glycosylation type IIs (ATP6AP1-CDG; OMIM# 300972) is a rare X-linked recessive complex syndrome characterized by liver dysfunction, recurrent bacterial infections, hypogammaglobulinemia, and defective glycosylation of serum proteins. Here, we examine the case of a 1-year-old male patient of Buryat origin, who presented with liver dysfunction. At the age of 3 months, he was hospitalized with jaundice and hepatosplenomegaly. Whole-exome sequencing identified the ATP6AP1 gene missense variant NM_001183.6:c.938A>G (p.Tyr313Cys) in the hemizygous state, which was previously reported in a patient with immunodeficiency type 47. At the age of 10 months, the patient successfully underwent orthotopic liver transplantation. After the transplantation, the use of Tacrolimus entailed severe adverse effect (colitis with perforation). Replacing Tacrolimus with Everolimus led to improvement. Previously reported patients demonstrated abnormal N- and O-glycosylation, but these data were collected without any specific treatment. In contrast, in our patient, isoelectric focusing (IEF) of serum transferrin was performed only after the liver transplant and showed a normal IEF pattern. Thus, liver transplantation could be a curative option for patients with ATP6AP1-CDG.

Functional Characterization of Two Novel Intron 4 SERPING1 Gene Splice Site Pathogenic Variants in Families with Hereditary Angioedema.

Variants that affect splice sites comprise 14.3% of all pathogenic variants in the SERPING1 gene; more than half of them are located outside the canonical sites. To make a clinical decision concerning patients with such variants, it is essential to know the exact way in which the effect of the variant would be realized. The optimal approach to determine the consequences is considered to be mRNA analysis. In the current study, we present the results of functional analysis of two previously non-described variants in the SERPING1 gene (NM_000062.3) affecting intron 4: c.686-1G>A and c.685+4dup, which were detected in members of two Russian families with autosomal dominant inheritance of angioedema type 1. Analysis of the patients' mRNA (extracted from whole blood) showed that the SERPING1(NM_000062.3):c.685+4dup variant leads to the loss of the donor splice site and the activation of the cryptic site in exon 4: r.710_745del (p.Gly217_Pro228del), while the SERPING1(NM_000062.3):c.686-1G>A variant leads to the skipping of exon 5: r.746_949del (p.Asp229_Ser296del).