Mutations In Wiskott-Aldrich Syndrome Gene Research Articles

Spectrum of WAS gene mutations in Vietnamese patients with Wiskott-Aldrich syndrome.

WAS gene mutational analysis is crucial to establish a definite diagnosis of Wiskott-Aldrich syndrome (WAS). Data on the genetic background of WAS in Vietnamese patients have not been reported. We recruited 97 male, unrelated patients with WAS and analyzed WAS gene mutation using Sanger sequencing technology. We identified 36 distinct hemizygous pathogenic mutations, with 17 novel variants, from 38 patients in the entire cohort (39.2%). The mutational spectrum included 14 missense, 12 indel, five nonsense, four splicing, and one non-stop mutations. Most mutations appear only once, with the exception of c.37C>T (p.R13X) and c.374G>A (p.G125E) each of which occurs twice in unrelated patients. Our data enrich the mutational spectrum of the WAS gene and are crucial for understanding the genetic background of WAS and for supporting genetic counseling.

Accelerated death of megakaryocytes from Wiskott-Aldrich syndrome patients.

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder caused by WAS gene mutations resulting in haematopoietic/immune cell defects. Recent studies report accelerated death of WAS platelets and lymphocytes. Data on megakaryocyte (MK) maturation, viability and their possible role in thrombocytopenia development in WAS are limited. In this study we evaluate the MK viability and morphology in untreated, romiplostim-treated WAS patients compared with normal controls. The study included 32 WAS patients and 17 healthy donors. MKs were captured from bone marrow aspirates by surface-immobilized anti-GPIIb-IIIa antibody. Viability (by phosphatidylserine [PS] externalization), distribution by maturation stages and size of MK were determined by light microscopy. MK distribution by maturation stages in patients differed from controls. 40 ± 22% of WAS MKs versus 23 ± 11% of normal MKs were at maturation stage 3 (p = 0.02), whereas 24 ± 20% in WAS and 39 ± 14% in controls had megakaryoblast morphology (p = 0.05). Romiplostim treatment changed the MK maturation stages distribution close to normal. PS-positive (PS+) MK in WAS was significantly higher (21 ± 21%) than in healthy controls (2 ± 4%, p < 0.01). WAS patients with more damaging truncating mutations and higher disease score had higher PS+ MK fraction (Spearman r = 0.6, p < 0.003). We conclude that WAS MKs have increased cell death tendency and changes in maturation pattern. Both could contribute to thrombocytopenia in WAS patients.

Wiskott-Aldrich syndrome caused by a novel mutation in the WAS gene and presenting with a mild phenotype

Background: Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder associated with combined immunodeficiency, microthrombocytopenia, eczema, and an increased risk of autoimmunity and cancer. Aim: To report the clinical presentation, immune features, and genetic mutation in a patient with a novel mutation in the Wiskott-Aldrich syndrome (WAS) gene, causing a mild phenotype of WAS. Methods: The patient’s chart was reviewed. We report the phenotypical and laboratory characteristics of a patient with a mild phenotype of WAS identified by WAS gene sequence analysis. Results: Our patient presented with thrombocytopenia and 3 episodes of otitis media at 24 months of age, with no other significant manifestations suggestive of immunodeficiency or immune dysregulation. A missense mutation was found in exon 12 of the WAS gene, C1498&gt;T, leading to a Trp500Arg amino acid change. Currently, he is 15 years old and remains in good health, free of infections or other complications to date. Conclusion: Genetic analysis is helpful for the diagnosis of WAS; our patient’s mutation was found to cause a mild phenotype. Statement of novelty: We describe a patient with a mild phenotype of WAS with a novel mutation in the WAS gene, thus, expanding the spectrum of WAS gene mutations.

ФЕНОМЕН БИМОДАЛЬНОЙ ЭКСПРЕССИИ БЕЛКА WASP У ПАЦИЕНТОВ С СИНДРОМОМ ВИСКОТТА–ОЛДРИЧА ПРИ ОЦЕНКЕ С ПОМОЩЬЮ ПРОТОЧНОЙ ЦИТОФЛУОРИМЕТРИИ

Compensatory or revertant somatic mutations (RSM) is a well-known phenomenon in patients with PIs. RSM can lead to the restoration of functional protein expression in some cell populations and thus influence the severity of clinical manifestations in patients with PI. The WAS gene, a mutation that leads to the development of Wiskott–Aldrich syndrome (WAS), is associated with high levels of RSM. In our study, we aimed to describe in detail the RSM phenomenon in patients with WAS, and also to try to study its effect on the severity of the clinical phenotype. Materials and methods of research: a single-center, prospective, open, continuous, non-randomized, comparative study was conducted. The study included 39 male patients with WAS from 2 months and up to 18 years old with mutation in WAS gene, who underwent assessment of WASP expression using flow cytometry. In 2 out of 9 patients, use of magnetic selection made it possible to isolate a population of lymphocytes expressing WASP. Germinal and somatic mutations were identified using Sanger sequencing. To assess severity of clinical manifestations of WAS, the original detailed scoring classification was used. Results: 9 patients had bimodal expression of WASP, which equaled to 23% of all examined. The median age of these patients was 3 years [7 months. – 15 years]. In two patients a presence of RSM was confirmed in WASP-expressing populations. Linear assessment of partially restored WASP expression revealed different patterns of lymphocyte subpopulation involvement in all 9 patients. The effect of RSM on the severity of clinical manifestations of WAS in the studied group of patients was statistically insignificant (p=0,39). Conclusion: according to the data obtained, patients with WAS, demonstrating a bimodal pattern of WASP expression, represent a very heterogeneous group in terms of the severity of clinical manifestations, involvement of cell populations, and the nature of RSM. This work is a methodological prerequisite for further comprehensive study of RSM phenomenon in patients with various PIs.

A novel splice site mutation in WAS gene in patient with Wiskott-Aldrich syndrome and chronic colitis: a case report

BackgroundWiskott-Aldrich syndrome is an X-linked recessive immunodeficiency due to mutations in Wiskott-Aldrich syndrome (WAS) gene. WAS gene is encoded for a multifunctional protein with key roles in actin polymerization, signaling pathways, and cytoskeletal rearrangement. Therefore, the impaired protein or its absence cause phenotypic spectrum of the disease. Since identification of novel mutations in WAS gene can help uncover the exact pathogenesis of Wiskott-Aldrich syndrome, the purpose of this study was to investigate disease causing-mutation in an Iranian male infant suspicious of this disorder.Case presentationThe patient had persistent thrombocytopenia from birth, sepsis, and recurrent gastrointestinal bleeding suggestive of both Wiskott-Aldrich syndrome and chronic colitis in favor of inflammatory bowel disease (IBD). To find mutated gene in the proband, whole exome sequencing was performed for the patient and its data showed a novel, private, hemizygous splice site mutation in WAS gene (c.360 + 1G > C).ConclusionsOur study found a novel, splice-site mutation in WAS gene and help consider the genetic counselling more precisely for families with clinical phenotypes of both Wiskott-Aldrich syndrome and inflammatory bowel disease and may suggest linked pathways between these two diseases.

Evaluation of Classic Wiskott Aldrich Syndrome with Mild Symptoms in Two Cousins: A Case Report

Introduction: Wiskott–Aldrich syndrome (WAS) is characterized by microthrombocytopenia, eczema, recurrent infections, and an increased incidence of autoimmunity. Commonly, classicWAS is presented with severe clinical symptoms. Case Presentation:We report a new phenotype of classic Wiskott–Aldrich syndrome with mild symptoms in two cousins who were 7 years old. They had not severe infections or hemorrhage, in spite of having genetic mutation in WAS gene. The symptoms and infections of the patients responded to treatment with IVIG and antibiotics. Conclusions: This report is presenting a novel clinical phenotype of classicWAS with milder symptoms.

Wiskott–Aldrich syndrome: Two case reports with a novel mutation

ABSTRACTBackground: The Wiskott–Aldrich syndrome (WAS) is X-linked recessive disorder associated with microplatelet thrombocytopenia, eczema, infections, and an increased risk of autoimmunity and lymphoid neoplasia. The originally described features of WAS include susceptibility to infections, microthrombocytopenia, and eczema.Aim: In this case report, we present our experience about two cases diagnosed with a new mutation.Methods: We report phenotypical and laboratory description of two cases with WAS.Results: We, for the first time, detected a new hemizygote mutation of WAS gene (NM_000377.2 p.M393lfs*102 (c.1178dupT)) in two patients. The first case was an 11-month-old boy presenting with complaints of recurrent soft tissue infection, ear infection, anemia, and thrombocytopenia with a low platelet volume. The second case was a 2-month-old boy presenting with thrombocytopenia and a low platelet volume. Both cases were the first-degree relatives: they were cousins and their mothers were sisters.Conclusion: Herein, we report two cases of WAS and a new gene mutation which would disrupt the WAS protein function within the Polyproline (PPP) domain. This report adds to the growing number of mutations which cause complex clinical manifestations associated with WAS.

A novel mutation of WAS gene in a boy with Mycobacterium bovis infection in spleen.

Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency disorder caused by mutations of the gene encoding WAS protein (WASp). A scoring system has been used to grade severity of the disease. However, the phenotype of the disease may progress over time, especially in children younger than 2 years of age. Here, we report a male child who presented with X-linked thrombocytopenia (XLT). Mutation analysis revealed a novel hemizygous 13-bp deletion (c.181_193delGCTGAGCACTGGA) on exon 2 of the WAS gene. This frameshift mutation resulted in a premature terminating codon at position 71 (p.A61fsX10). Molecular analysis of maternal DNA revealed a heterozygosity of the same mutation. The disease progressed to classic WAS within 8 months. Later, gastric varices as a consequence of Mycobacterium bovis infection in the spleen was detected. The rapid worsening of the disease may be due to the severe genotype of this patient.

Wiskott-Aldrich Syndrome With Normal-Sized Platelets in an Eighteen-Month-Old Boy: A Rare Mutation

Introduction: Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by thrombocytopenia, eczema, and recurrent infections. The disease is usually associated with small defective platelets. Case Presentation: We described an 18-month-old boy who presented with lower gastrointestinal bleeding, eczema, and recurrent infections. There was pancytopenia with normal-sized platelets. In addition, the CD4 count was significantly low and serum IgA and IgE levels were increased. The diagnosis of WAS was confirmed by detecting a mutation of WAS gene, which was due to a deletion mutation resulting in frameshift (c.177DelT). Conclusions: Usually microplatelets with mean platelet volume of 4-5 fL are seen in WAS, but in this case, the patient had normal-sized platelets with a rare mutation of WAS gene. Therefore, high index of clinical suspicion is needed to diagnose WAS.

Newborn screening for severe T and B cell lymphopenia identifies a fraction of patients with Wiskott–Aldrich syndrome

The lack or marked reduction of recently formed T and B cells provides a basis for neonatal screening for severe combined immunodeficiencies (SCID) and X-linked agammaglobulinemia (XLA). Newborns with other conditions are also identified if a severe T or B cell lymphopenia is present at birth. We retrospectively analyzed Guthrie card samples from 11 children with Wiskott–Aldrich syndrome (WAS), a rare disease that requires early diagnosis and treatment, to determine whether combined T-cell receptor excision circle (TREC) and kappa-deleting recombination excision circle (KREC) screening could identify these patients. 4 of 11 patients showed markedly reduced TREC or KREC copy numbers in their DBS as compared to storage-time matched controls and prospectively screened Swedish and German newborns. No correlation was observed between the WAS gene mutations, the clinical severity/course and the result of the screening assay. A diagnosis of WAS should thus be considered in newborns with positive TREC or KREC screening results.

T-cell receptor diversity is selectively skewed in T-cell populations of patients with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is a severe disorder characterized by thrombocytopenia, eczema, immunodeficiency, and increased risk of autoimmune disease and lymphoid malignancies. The immunodeficiency caused by a lack of WAS protein expression has been mainly attributed to defective T-cell functions. Whether WAS mutations differentially influence the T-cell receptor (TCR) diversity of different T-cell subsets is unknown. We aimed to identify the degree and pattern of skewing in the variable region of the TCR β-chain (Vβ) in different T-cell subsets from patients with WAS. The TCR repertoire diversity in total peripheral Tcells, sorted CD4(+) and CD8(+) T cells, and CD45RA(+) (CD45RA(+)CD45RO(-) cells) and CD45RO(+) (CD45RA(-)CD45RO(+) cells) CD4(+) and CD8(+) T cells from patients with WAS and age-matched healthy control subjects was analyzed and compared by using spectratyping of complementarity-determining region 3. The complementarity-determining region 3 of TCRβ transcripts in CD45RA(+)CD4(+) and CD45RA(+)CD8(+) T cells, CD45RO(+)CD4(+) T cells, CD8(+) terminally differentiated effector memory T (Temra) cells, and naive CD8(+) T cells (CD8(+)CD45RO(-)CCR7(+) cells) from patients and control subjects were analyzed and compared by using high-throughput sequencing. The TCR repertoire diversity in CD45RO(+)CD4(+) T cells and CD8(+) Temra cells of patients with WAS was significantly skewed in comparison with that seen in age-matched control subjects. Our results indicate that WAS gene mutations selectively influence TCR repertoire development or expansion in CD45RO(+) (memory) CD4(+) T cells.

Two cases of wiskott–Aldrich syndrome in neonates due to gene mutations

Wiskott–Aldrich syndrome (WAS) is a rare X-linked recessive disease characterized by eczema, thrombocytopenia and immune deficiency. WAS gene mutations impair WAS protein function which cause WAS. The WAS-related disorders of X-linked thrombocytopenia (XLT) and X-linked congenital neutropenia (XLN) may have similar but less severe symptoms those are also caused by mutations of the same gene. We present two cases of WAS in neonates with WAS gene mutations. Early genetic diagnosis can help to the treatment and prevention this disease.

Clinical spectrum, pathophysiology and treatment of the Wiskott–Aldrich syndrome

The Wiskott-Aldrich syndrome (WAS), caused by mutations in the WAS gene, is a complex and diverse disorder with X-linked inheritance. This review focuses on recent developments in the understanding of its basic pathophysiology, diverse clinical phenotypes and optimal patient management including novel therapies. The protein encoded by the WAS gene is a multifunctional signaling element expressed in immune and hematopoietic cells that plays a critical role in cytoskeletal reorganization, immune synapse formation and intracellular signaling. The type of specific mutation, its location within the gene and its effect on protein expression play a major role in determining an individual patient's clinical phenotype. Recent clinical observations and molecular studies have created a sophisticated picture of the disease spectrum. The improved outcome of stem cell transplantation from related and unrelated matched donors and promising early results from the first clinical gene therapy trial have added new therapeutic options for these patients. Classic WAS, X-linked thrombocytopenia and X-linked neutropenia are caused by WAS gene mutations, each having a distinct pattern of clinical symptoms and disease severity. New developments in the understanding of these syndromes and novel therapeutic options will have a major impact on the treatment of individuals with WAS mutations.

X-linked thrombocytopenia (XLT) due to WAS mutations: clinical characteristics, long-term outcome, and treatment options

AbstractA large proportion of patients with mutations in the Wiskott-Aldrich syndrome (WAS) protein gene exhibit the milder phenotype termed X-linked thrombocytopenia (XLT). Whereas stem cell transplantation at an early age is the treatment of choice for patients with WAS, therapeutic options for patients with XLT are controversial. In a retrospective multicenter study we defined the clinical phenotype of XLT and determined the probability of severe disease-related complications in patients older than 2 years with documented WAS gene mutations and mild-to-moderate eczema or mild, infrequent infections. Enrolled were 173 patients (median age, 11.5 years) from 12 countries spanning 2830 patient-years. Serious bleeding episodes occurred in 13.9%, life-threatening infections in 6.9%, autoimmunity in 12.1%, and malignancy in 5.2% of patients. Overall and event-free survival probabilities were not significantly influenced by the type of mutation or intravenous immunoglobulin or antibiotic prophylaxis. Splenectomy resulted in increased risk of severe infections. This analysis of the clinical outcome and molecular basis of patients with XLT shows excellent long-term survival but also a high probability of severe disease-related complications. These observations will allow better decision making when considering treatment options for individual patients with XLT.

Molecular Analysis of WASP Gene - First Report from India.

Wiskott Aldrich Syndrome (WAS) is an X-linked recessive disorder associated with severe thrombocytopenia, eczema, bloody diarrhea, profound immunodeficiency and an increased risk of malignancies. More than 200 mutations have been described in the gene encoding the WAS protein (WASP). We report here the molecular basis of WAS in six patients from India. Diagnosis of WAS/X- linked thrombocytopenia (XLT) was based on low platelet count (9000– 1, 25,000/mm3), presence of small platelets (mean: 6.2fl) and detection of WASP by flowcytometry. Patients evaluated in the study could be classified as classical WAS (n=3) and XLT (n=3) depending on the clinical severity of their disease (Zhu et.al 1995). All 12 exons and flanking splice-sites of WAS gene were amplified by polymerase chain reaction (PCR) using primers and PCR conditions adopted with modifications from Kwan et al (PNAS 1995; 92:4706). Mutation analysis was accomplished by conformation sensitive gel electrophoresis (CSGE) and direct sequencing. Abnormal banding pattern was observed only in 4 patients after CSGE analysis. c.995 C>T could not be detected by CSGE but was detected by direct sequencing. The types of molecular defects identified in five patients were as follows: nonsense - 2, deletion - 1 and duplication - 1. Three of these alterations (see table) have been reported previously and are associated with classical WAS. In patients detected to have nonsense mutations, flowcytometric analysis of WASP exhibited high values (table) not consistent with reported western blotting data in these mutations. c.307+10-11dupC was observed in two patients (brothers) with thrombocytopenia, small platelets and mild bleeding. This duplication is not a reported polymorphism. Though this duplication changes the acceptor splice site prediction score from 0.83 to 0.91, its functional significance has not been determined and requires further evaluation. The sixth patient in our study had thrombocytopenia (15,000–45,000/mm3), small platelets (4.8–7.2 fl), mild bleeding, similar family history and normal expression of WASP (86.2%). No mutation has been identified in the coding region of WAS gene in this patient either by CSGE or direct sequencing. Our data shows that the molecular basis for WAS is heterogenous in India. This is the first study evaluating mutations in WAS gene from India. Further mutation screening of patients with WAS will allow the genetic definition, phenotype-genotype corelation, carrier detection and prenatal diagnosis of this condition.Molecular defects observed in WAS patientsPatient IDFlow cytometry (%)MutationPD-22WASP D1-98.5, WASPB9 - 94.8c.665C>T, p.Arg211X*PD-16WASP B9- 6.7c. 1035-1036 delG, p.Gly314ValfsX120*PD-21WASP D1-97.2, WASP B9-91.2c.995 C>T, p. Arg321X*PD-34, PD-35 (siblings)WASP D1-3.6, WASP B9-2; D1-1.8, B9-1c.307+10-11 dupC♦PD-28WASP D1 - 86.2Mutation not detected*-Reported mutation, ♦-Functional Significance not known

A Familial Case of Wiskott-Aldrich Syndrome with a Hotspot Mutation in Exon 2 of the WAS Gene

The Wiskott-Aldrich syndrome (WAS) is a severe X-linked disorder characterized classically by thrombocytopenia, immunodeficiency, and eczema. The phenotype observed in this syndrome is caused by mutation in the WAS gene. Peripheral blood DNAs were isolated from an 18-month-old boy with WAS and his mother, maternal uncle, and maternal grandmother. Genetic analysis for the detection of a mutation of WAS gene was performed by polymerase chain reaction-single strand conformational polymorphism analysis (PCR-SSCP) and direct sequencing of the PCR product. In PCR-SSCP, the patient and his maternal uncle had an abnormal shift band, which was not found in normal controls, and his mother and maternal grandmother showed heterozygous bands. In direct sequencing analysis, the patient with WAS had CGC→CAC point mutation in exon 2 that resulted in an amino acid change in codon 86 (Arg86His). The present study identified a gene mutation responsible for WAS at a mutation hotspot of the WAS gene in a Korean family.

A novel termination codon mutation of the WAS gene in a Thai family with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by microthrombocytopenia, eczema, immunodeficiency, and susceptibility to lymphoid malignancy. Loss-of-function mutations in WAS gene have been identified to cause disorders with platelet defects including WAS and X-lined thrombocytopenia. Mutations anticipated to yield truncated or no protein have been associated with the more severe presentations of WAS. Activating mutations in WAS gene result in an entirely different phenotype, an X-linked severe congenital neutropenia. Case report We describe a Thai family with classic WAS. The proband, a one-year-old boy presented with recurrent mucous bloody diarrhea, recurrent otitis media, chronic eczema, thrombocytopenia, and small platelet sizes, the patient's older brother who was also had persistent thrombocytopenia died at the age of seven months from severe pneumonia. Immunoblot analysis demonstrated that the proband's cells lacked WAS protein expression. Mutation analysis of the proband and his mother for the entire coding region of WAS identified a novel type of mutation, a termination codon mutation, X503R. The change is expected to result in an elongated mRNA that would code for a WASP of 581 amino acid residues instead of the normal 502 residues. Because of the absence of WASP expression, we speculated that the termination codon mutation causes reduced mRNA stability. Conclusion Our finding supported that WAS mutations resulted in no protein are associated with a severe phenotype of WAS.

A novel termination codon mutation of the WAS gene in a Thai family with Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by microthrombocytopenia, eczema, immunodeficiency, and susceptibility to lymphoid malignancy. Loss-of-function mutations in WAS gene have been identified to cause disorders with platelet defects including WAS and X-linked thrombocytopenia. Mutations anticipated to yield truncated or no protein have been associated with the more severe presentations of WAS. Activating mutations in WAS gene result in an entirely different phenotype, an X-linked severe congenital neutropenia. We describe a Thai family with classic WAS. The proband, a one-year-old boy presented with recurrent mucous bloody diarrhea, recurrent otitis media, chronic eczema, thrombocytopenia, and small platelet sizes. The patient's older brother who also had persistent thrombocytopenia died at the age of seven months from severe pneumonia. Immunoblot analysis demonstrated that the proband's cells lacked WAS protein expression. Mutation analysis of the proband and his mother for the entire coding region of WAS identified a novel type of mutation, a termination codon mutation, X503R. The change is expected to result in an elongated mRNA that would code for a WASP of 581 amino acid residues instead of the normal 502 residues. Because of the absence of WASP expression, we speculate that the termination codon mutation causes reduced mRNA stability. Our findings supported that WAS mutations resulted in no protein are associated with a severe phenotype of WAS.

Wiskott-Aldrich syndrome in Argentina: 17 unique, including nine novel, mutations.

Wiskott-Aldrich syndrome (WAS), is an X-linked immunodeficiency disease caused by mutations of the WAS protein (WASP) gene, characterized by thrombocytopenia, eczema and recurrent infections. X-linked thrombocytopenia (XLT) is a milder form with only platelet abnormalities. Cumulative mutation data have revealed that WASP genotypes are highly variable among WAS patients. By SSCP analysis, we determined the location of the mutation in 23 WAS patients from 17 unrelated families with variable clinical phenotypes. Direct sequence analysis of genomic DNA showed 9 novel mutations (Q52H, G70W, 393del7, Ex 7 Ex11del, IVS 8+1G-->C, 925delG, 959ins38, 1380del8, and IVS 2+2T-->C) and 8 known mutations distributed throughout the WAS gene. This is the first report of WAS gene mutations from a Latin American country.

Unique and Recurrent WAS Gene Mutations in Wiskott-Aldrich Syndrome and X-Linked Thrombocytopenia

ABSTRACT: Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT) are allelic phenotypes caused by defects of the WAS gene. Fourteen distinct mutations including seven novel gene defects in 16 WAS and four XLT patients were identified by single strand conformation polymorphism analysis and DNA sequencing of the WAS gene. Eleven (79%) of these mutations are located within exons 1 to 4 with clustering in exon 2. Carrier detection in 33 at-risk females and prenatal diagnosis at 12 weeks gestation in one family with a novel WAS mutation was performed by direct mutation analysis. A remarkably high frequency (72%) of point mutations involved CpG dinucleotides. C→T or G→A transitions at CpG sites were identified in all isolated WAS cases (n=7). Allele frequencies for the dinucleotide repeat at locus DXS6940 were determined in Northern European, African and Asian populations. Mutation screening alone or in combination with analysis of polymorphic loci DXS6940 and DXS255 delineated the germline origin of a unique insertion mutation and four recurrent CpG mutations, three of which arose spontaneously during maternal gametogenesis.