Genetic mutation analysis in three pedigrees with hereditary multiple exostosis / 中华检验医学杂志

Objective:To detect the pathogenic gene of the three pedigrees with hereditary multiple exostosis, and to provide evidences for genetic counselling and prenatal diagnosis.Methods:The three families were admitted to the Institute of Medical Genetics of Henan Provincial People′s Hospital due to hereditary multiple exostosis from January 2018 to December 2020. Detail medical history and the blood samples of the family members were collected after they signed the informed consent forms. The pathological mutations were selected from the proband using whole exome sequencing (WES). Sanger sequencing was used to conduct the co-segregation analysis of the family members. The pathogenicity of the mutation was analyzed in combination with ACMG guidelines.Results:The EXT1 gene c.1056+2T>C mutation, c.369dupA (p.G124fs) mutation and the EXT2 gene c.1171C>T (p.Q391*) mutation were detected in the probands through whole exome sequencing. The same mutations were found in the patients from these three families, while the mutation was not detected among the healthy family members. These variations have co-segregated with the disease phenotype. According to ACMG guidelines, all mutations in these three families meet the criteria of pathogenic variations. Conclusion:The EXT1 gene c.1056+2T>C mutation, c.369dupA (p.G124fs) mutation and the EXT2 gene c.1171C>T (p.Q391*) mutation were identified to be responsible for hereditary multiple exostosis in these families.

Exostosis múltiple hereditaria: reporte de una familia / Hereditary multiple exostoses: report of a family

FUNDAMENTO: el osteocondroma es el tumor óseo benigno frecuente en la edad pediátrica y la exostosis múltiple hereditaria en sus variedades, con un patrón de herencia autosómica dominante, con distribución simétrica por casi todo el esqueleto, aunque puede existir distribución asimétrica en dos de los tres genotipos de la enfermedad. OBJETIVO: presentar una familia portadora de exostosis múltiple hereditaria, diagnosticada de forma multidisciplinaria, por aspectos clínicos, radiológicos e histopatológicos. CASO CLINICO: se presenta un caso de una familia con malformaciones músculos esqueléticos. Predominó la estatura baja y las lesiones nodulares duras no dolorosas en brazos, antebrazos, muslos, piernas, costillas y escápulas, con deformidades en regiones proximales y distales en ambos brazos, antebrazos; así como en tercio proximal y distal de las piernas. En las radiografías se observaron lesiones en la diáfisis de los huesos afectados de diferentes aspectos, ovaladas, lobuladas y alargadas, las cuales están bien delimitadas. A todos los pacientes se les realizó exámenes de laboratorio, los cuales fueron normales y recibieron tratamiento quirúrgico con resección de las tumoraciones más prominentes y las que presentaron mayor tendencia a la malignización, como son las de las costillas, escápula, pelvis y hombros. CONCLUSIONES: la exostosis múltiple hereditaria se considera una enfermedad poco frecuente en nuestro medio y el tratamiento de elección es el quirúrgico para mejorar las manifestaciones clínicas.

BACKGROUND: osteochondroma is the most common benign osseous tumor in pediatric age and hereditary multiple exostoses is one of its types with a pattern of dominant autosomal heredity and a symmetrical distribution in almost all the skeleton, although an asymmetrical distribution can appear in two of the three genotypes of the disease. OBJECTVE: to present the case of a family that suffers from hereditary multiple exostoses diagnosed in a multidisciplinary way from clinical, radiological, and histopathological aspects. CLINICAL CASE: the case of a family with muscular-skeletal malformations is presented. Short height predominated, as well as non-painful hard nodular lesions in arms, forearms, thighs, legs, ribs, and scapulas with deformities in proximal and distal areas in both arms and forearms and in the proximal and distal third of the legs. From the radiological point of view, lesions of different aspects (oval, lobate, elongated) and of well-defined appearance were observed in the diaphysis of the affected bones. All the patients underwent laboratory exams, the results of which were normal. The patients underwent surgical treatment with removal of the most prominent tumors and mainly those which presented a greater tendency to become malignant, like rib, scapula, pelvis and shoulder. CONCLUSIONS: hereditary multiple exostoses constitute an infrequent illness in our environment and surgical treatment is the best choice to improve the clinical manifestations.

A novel splice mutation in EXT1 gene of hereditary multiple osteochondroma and analysis of its pathogenic mechanism / 中华检验医学杂志

Objective To analyse a novel splice mutation in EXT1 gene of hereditary multiple osteochondroma, and study its pathogenic mechanism.Methods In April of 2013, the proband was hospitalized from the outpatient department with multiple joint deformity for more than 20 years, peripheral blood of the proband and his parents were collected and genomic DNA was extracted .Coding regions and adjacent intron sequences of EXT1/EXT2 genes in genomic DNA of the family members were amplified and sequenced.Bioinformatics was used to analyze the mutation from sequencing .cDNA from peripheral blood of the proband ,the mother and normal control was made respectively as a template for amplifying coding regions of EXT1 gene, and the product was T-A cloned and sequenced.The abnormal transcripts of each group were counted and analyzed using chi square test to study the pathogenic mechanism of the mutation .Results Sequencing results of family members revealed that there was a heterozygous deletion mutation ( c.1284 +2del) in the 5′splice site of intron 4 in EXT1 gene of the proband and his mother .Bioinformatics predicted that exon 4 of EXT1 gene was skipping or spliced aberrantly due to the mutation .T-A clone and sequencing results as well as the statistical analysis suggested that there was a significantly higher proportion of transcripts with skipping exon 4 in the proband and his mother compared with the normal control (P=0.000, P<0.01).Conclusions c.1284+2del in EXT1 gene is reported for the first time internationally , which results in a considerable number of abnormal transcripts with skipping exon 4 in EXT1 gene, thereby influences the normal transcription and translation of EXT1 gene.

Gene mutation screening and the genotype-phenotype correlation of hereditary multiple exostoses / 中华检验医学杂志

Objective To establish the method of gene mutation screening for HME and investigate the relationship between genotype and clinical phenotype in HME patients. Methods Fifteen cases of HME probands were divided into the following four subgroups: mild (M) and severe ( Ⅰ S, Ⅱ S, Ⅲ S) according to the clinical diagnosis. DNA samples were obtained from the probands and family members. All of the EXT1 and EXT2 gene exons and their boundary sequences were amplified by PCR, and sequenced by directsequencing. Then the relationship between the genotypes and clinical phenotype was analyzed. Results Among the fifteen cases of HME probands, nine harbored EXT1 gene mutation, while the other 6 were positive for EXT2 gene mutation. Moreover, six novel mutations in EXT1 gene, including I8 + 2T ＞ G, c. 1182delG,c. 1108G ＞T(p. E370X) ,c. 335delA,c. 361C ＞T(p. Q121X) and c. 1879_1881delCAC were identified. In 9 patients with EXT1 gene mutation, 2 (22. 2% ) were M-type, 2 (22. 2% ) were Ⅰ S -type, 4 (44. 4% )were Ⅱ S-type,and 1 ( 11.1% ) was ⅢS-type. Whereas, 5 cases (83.3%) were M-type and only one case was Ⅱ S-type( 16. 7% ) in 6 patients with EXT2 gene mutation. Conclusions An accurate and simple gene diagnostic method for HME was established. Six novel EXT1 gene mutations, including I8 + 2T ＞ G,c. 1182delG, c. 1108G ＞T(p. E370X), c. 335delA, c. 361C ＞T(p. Q121X)and c. 1879_1881delCAC were identified as well. The clinical phenotype of the patients with EXT1 gene mutation was more severe compared to those with EXT2 gene mutations.