Hypofibrinogenaemia with Compound Heterozygosity for Two γ Chain Mutations – γ 82 Ala→Gly and an Intron Two GT→AT Splice Site Mutation

SummaryWe investigated the molecular basis of hypofibrinogenaemia in a woman with a history of recurrent, pregnancy-associated bleeding, and miscarriage. She had a Clauss fibrinogen of 0.9 mg/ml and SDS PAGE of purified fibrinogen showed a normal pattern of chains. However careful inspection of reverse phase chain separation profiles showed apparent homozygosity for a more hydrophilic form of the γ chain. DNA Sequencing showed only heterozygosity for a CGT→GGT (Ala→Gly) mutation at codon γ82, but further sequencing showed an additional GT splice sequence mutation at the 5’ end of intron 2 of the γ gene. Translation of mRNA containing this intron would result in premature truncation explaining the phenotypic homozygosity of the γ82 Ala→Gly substitution. The patient’s sister had a mild bleeding disorder with hypofibrinogenaemia and she too was a compound heterozygote for the γ mutations. Her nephew had only the novel splice site mutation, while her mother and daughter inherited only the γ82 Ala→Gly substitution.

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Somatic mosaicism and compound heterozygosity in female hemophilia B

Blood ◽

10.1182/blood.v96.4.1585 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1585-1587 ◽

Cited By ~ 17

Author(s):

Jean-Marc Costa ◽

Dominique Vidaud ◽

Ingrid Laurendeau ◽

Michel Vidaud ◽

Edith Fressinaud ◽

...

Keyword(s):

Splice Site ◽

Somatic Mosaicism ◽

Splice Site Mutation ◽

Factor Ix ◽

Hemophilia B ◽

Hemorrhagic Diathesis ◽

Site Mutation ◽

History Of ◽

Sporadic Cases ◽

In Trans

Abstract Sequencing the complete factor IX gene of 2 sisters with hemophilia B with different phenotypes and no family history of hemorrhagic diathesis revealed a common 5′ splice site mutation in intron 3 (T6704C) in both and an additional missense mutation (I344T) in one. The presence of dysfunctional antigen in the latter strongly suggested that these mutations are in trans. Neither mutation was found in leukocyte DNA from the asymptomatic parents, but the mother was in somatic mosaicism for the shared splice site mutation. This case illustrates the importance of defining the phenotype and considering somatic mosaicism in sporadic cases. It underlines the limitations of complete gene sequencing for the detection of mosaicism and has implication for genetic counseling.

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Predicting Phenotype in Steroid 21-Hydroxylase Deficiency? Comprehensive Genotyping in 155 Unrelated, Well Defined Patients from Southern Germany

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jcem.85.3.6441 ◽

2000 ◽

Vol 85 (3) ◽

pp. 1059-1065 ◽

Cited By ~ 147

Author(s):

Nils Krone ◽

Andreas Braun ◽

Adelbert Anton Roscher ◽

Dietrich Knorr ◽

Hans Peter Schwarz

Keyword(s):

Splice Site ◽

Splice Site Mutation ◽

Compound Heterozygous ◽

Site Mutation ◽

Hydroxylase Deficiency ◽

Salt Wasting ◽

Severe Mutation ◽

Heterozygous Form ◽

21 Hydroxylase Deficiency ◽

Intron 2

Abstract Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders. CAH is most often caused by deficiency of steroid 21-hydroxylase. The frequency of CYP21-inactivating mutations and the genotype-phenotype relationship were characterized in 155 well defined unrelated CAH patients. We were able to elucidate 306 of 310 disease-causing alleles (diagnostic sensitivity, 98.7%). The most frequent mutation was the intron 2 splice site mutation (30.3%), followed by gene deletions (20.3%), the I172N mutation (19.7%) and large gene conversions (7.1%). Five point mutations were detected that have not been described in other CAH cohorts. Genotypes were categorized in 4 mutation groups (null, A, B, and C) according to their predicted functional consequences and compared to the clinical phenotype. The positive predictive value for null mutations (ppvnull) was 100%, as all patients with these mutations had a salt-wasting phenotype. In mutation group A (intron 2 splice site mutation in homozygous or heterozygous form with a null mutation), the ppvA to manifest with salt-wasting CAH was 90%. In group B predicted to result in simple virilizing CAH (I172N in homozygous or compound heterozygous form with a more severe mutation), ppvB was 74%. In group C (P30L, V281L, P453S in homozygous or compound heterozygous form with a more severe mutation), ppvC was 64.7% to exhibit the nonclassical form of CAH, but 90% when excluding the P30L mutation. Thus, in general, a good genotype-phenotype relationship is shown in patients with either the severest or the mildest mutations. A considerable degree of divergence is observed within mutation groups of intermediate severity. As yet undefined factors modifying 21-hydroxylase gene expression and steroid hormone action are likely to account for these differences in phenotypic expression.

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Somatic mosaicism and compound heterozygosity in female hemophilia B

Blood ◽

10.1182/blood.v96.4.1585.h8001585_1585_1587 ◽

2000 ◽

Vol 96 (4) ◽

pp. 1585-1587

Author(s):

Jean-Marc Costa ◽

Dominique Vidaud ◽

Ingrid Laurendeau ◽

Michel Vidaud ◽

Edith Fressinaud ◽

...

Keyword(s):

Splice Site ◽

Somatic Mosaicism ◽

Splice Site Mutation ◽

Factor Ix ◽

Hemophilia B ◽

Hemorrhagic Diathesis ◽

Site Mutation ◽

History Of ◽

Sporadic Cases ◽

In Trans

Sequencing the complete factor IX gene of 2 sisters with hemophilia B with different phenotypes and no family history of hemorrhagic diathesis revealed a common 5′ splice site mutation in intron 3 (T6704C) in both and an additional missense mutation (I344T) in one. The presence of dysfunctional antigen in the latter strongly suggested that these mutations are in trans. Neither mutation was found in leukocyte DNA from the asymptomatic parents, but the mother was in somatic mosaicism for the shared splice site mutation. This case illustrates the importance of defining the phenotype and considering somatic mosaicism in sporadic cases. It underlines the limitations of complete gene sequencing for the detection of mosaicism and has implication for genetic counseling.

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A Novel splice-site mutation on the MLC1 gene leading to exon 9 skipping and megalencephalic leukoencephalopathy with subcortical cysts in a Turkish patient

Balkan Journal of Medical Genetics ◽

10.2478/bjmg-2019-0019 ◽

2019 ◽

Vol 22 (2) ◽

pp. 89-92

Author(s):

A Türkyılmaz ◽

O Ünver ◽

G Ekinci ◽

D Türkdoğan

Keyword(s):

Splice Site ◽

Brain Magnetic Resonance Imaging ◽

Splice Site Mutation ◽

The Novel ◽

Site Mutation ◽

Turkish Patient ◽

Neurology Clinic ◽

Exon 9 ◽

Magnetic Resonance Imaging Mri ◽

Subcortical Cysts

AbstractMegalencephalic leukoencephalopathy (MLC) with subcortical cysts, also known as Van der Knaap disease (MIM #604004) is an autosomal recessive neurological disorder characterized by early onset macrocephaly, epilepsy, neurological deterioration with cerebellar ataxia and spasticity. An 8-month-old boy was admitted to our pediatric neurology clinic with macrocephaly. His brain magnetic resonance imaging (MRI) revealed bilateral, diffuse, symmetric structural white matter abnormalities, relatively sparing the cerebellum and bilateral subcortical temporal cysts. The diagnosis of Van der Knaap disease was suspected based on the clinical features and imaging findings and the genetic analysis revealed a novel homozygous c.768+2T>C mutation of the MLC1 gene. For determination of the novel splice-site mutation’s effect, cDNA amplification was performed. cDNA analysis showed that the splice-site c.768+2T>C mutation gave rise to exon 9 skipping.

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Novel Splice Site Mutation in the PROS1 Gene in a Polish Patient with Venous Thromboembolism: c.602-2delA, Splice Acceptor Site of Exon 7

Medicina ◽

10.3390/medicina56090485 ◽

2020 ◽

Vol 56 (9) ◽

pp. 485

Author(s):

Magdalena Mrożek ◽

Ewa Wypasek ◽

Martine Alhenc-Gelas ◽

Daniel P. Potaczek ◽

Anetta Undas

Keyword(s):

Venous Thromboembolism ◽

Sequence Analysis ◽

Splice Site ◽

Splice Site Mutation ◽

Splice Acceptor Site ◽

Acceptor Site ◽

Nucleotide Position ◽

Splice Acceptor ◽

Site Mutation ◽

History Of

We identified a novel splice site mutation of the PROS1 gene in a Polish family with protein S (PS) deficiency and explored the molecular pathogenesis of this previously undescribed variant. A novel mutation was detected in a 26-year-old woman with a history of venous thromboembolism (VTE) provoked by oral contraceptives. Her family history of VTE was positive. The sequence analysis of the PROS1 gene was performed in the proband and the proband’s family. The proband and their asymptomatic father had lower free PS levels (45% and 50%, respectively) and PS activity (48% and 44%, respectively). Total PS levels were normal (65.6% and 62.4%, respectively). The sequence analysis of the PROS1 gene revealed the presence of heterozygous deletion at the nucleotide position c.602-2 in intron 6, just upstream of exon 7, detected in the proband and her father. This variant alters the splice acceptor site of exon 7, and, according to the in silico prediction, it is highly likely to cause in-frame exon 7 skipping. We also presented follow-up data of two other Polish patients with PS deficiency associated with splice site mutations in PROS1 gene.

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