Detection rate and clinical significance of regions of homozygosity in prenatal genetic diagnosis / 中华妇产科杂志

Objective:To detect the incidence and analyze the clinical significance of regions of homozygosity (ROH) through the single nucleotide polymorphism array (SNP array).Methods:The SNP array detection results of 5 116 pregnant women in the Third Affiliated Hospital of Guangzhou Medical University from January 2016 to December 2020 were retrospectively analyzed. The pregnant women with ROH (5 Mb as the threshold) were followed up to analyze the relationship between ROH and abnormal fetal phenotype. Whole exon sequencing was performed in 4 cases of consanguineous marriage to detect potential recessive causative genes in the ROH region.Results:(1) A total of 39 cases of ROH were detected, with a positive rate of 0.76% (39/5 116). Among them, 25 cases (64%, 25/39) were detected only on single chromosome, and chromosome 11 had the highest detection rate, suggesting the risk of uniparental disomy; fourteen cases (36%,14/39) were detected on multiple chromosomes, most commonly on chromosomes 11, 1, 3, 4 and 8. (2) The number of cases and detection rate of ROH detected by different prenatal diagnosis indicators were as follows: 12 cases (1.78%, 12/676) in pregnant women with abnormal non-invasive prenatal testing result, 12 cases (0.37%, 12/3 284) in pregnant women with ultrasound abnormality, 4 cases (4/4) in pregnant women with consanguineous marriage, 3 cases (0.92%, 3/326) in pregnant women with previous adverse pregnancy, 2 cases (1.15%, 2/174) in pregnant women with high risk of serology in screening, 2 cases (4.00%, 2/50) in pregnant women with abnormal fetal chromosomal karyotype, 2 cases (0.79%, 2/253) in pregnant women with advanced maternal age, 1 case (0.56%, 1/178) in pregnant women with related parental genetic factors and 1 case (0.58%, 1/171) in pregnant women with the other factors. (3) The follow-up results of 39 cases of prenatal ROH showed that there were 16 cases of term birth, 15 cases of termination of pregnancy, 2 cases of preterm births, 1 case of fetal death and 5 cases lost to follow-up.Conclusions:Chromosomal ROH phenomenon is not rare. By analyzing the detection rate of ROH in prenatal diagnosis, combined with the results of fetal phenotype and postpartum follow-up, the clinical characteristics of ROH are discussed, so as to better understand the relationship between ROH and its phenotype.

Impacto de la consanguinidad en la descendencia de matrimonios consanguíneos / Impact of Consanguinity in the Offspring of Consanguineous Marriages

Introducción: La consanguinidad continúa siendo un fenómeno universal, hoy día los matrimonios consanguíneos y su descendencia suponen aproximadamente el 10,4 por ciento de la población mundial; sus descendientes tienen una elevada probabilidad de padecer enfermedades mendelianas recesivas, así como enfermedades complejas de naturaleza multifactorial. Objetivos: Determinar el coeficiente de endogamia de la región y las principales afectaciones encontradas en la descendencia de matrimonios consanguíneos. Métodos: Se realizó una investigación descriptiva, aplicada y retrospectiva de corte transversal sobre coeficiente de endogamia en el Consejo Popular Paso Quemado, municipio Los Palacios, Pinar del Río, en el período comprendido entre mayo 2016 y febrero 2017. Resultados: Fueron identificados 11 matrimonios consanguíneos (1,96 por ciento), mayormente en área rural y entre primos hermanos. El coeficiente de endogamia medio fue 0,00115. Después de la década del 70 no se efectuaron matrimonios consanguíneos. Afectaciones como mortalidad infantil, enfermedades monogénicas raras, malformaciones congénitas, discapacidad intelectual leve y enfermedades comunes aparecieron con mayor frecuencia en la descendencia de primos hermanos. Conclusiones: En correspondencia con la apertura de nuevas oportunidades sociales, económicas y educativas en la región la consanguinidad no constituye hoy en día un problema de salud, no obstante 52,5 por ciento de la descendencia en consanguíneos resultó afectada, mayormente por enfermedades complejas. El estudio sienta las bases para establecer una estrategia de educación y promoción de salud a nivel comunitario(AU)

Introduction: Consanguinity continues to be a universal phenomenon. Nowadays, consanguineous marriages and their descendants are estimated at 10,4 percent of the world population; their descendants have a high probability of suffering recessive Mendelian diseases, as well as complex diseases of multifactorial nature. Objectives: To determine the inbreeding coefficient of the region and the main affectations found in offspring of consanguineous marriages. Methods: A descriptive, applied and retrospective cross-sectional research on the inbreeding coefficient was conducted at Paso Quemado Popular Council, Los Palacios Municipality, Pinar del Río, from May 2016 to February 2017. Results: We identified 11 consanguineous marriages (1.96 percent), mostly in rural areas and among first cousins. The average inbreeding coefficient was 0.00115. After the 70's, there was no occurrence of consanguineous marriages. Affectations such as infant mortality, rare monogenic diseases, congenital malformations, mild intellectual disability and common diseases appeared more frequently in the offspring of first cousins. Conclusions: In correspondence with the opening of new social, economic and educational opportunities in the region, consanguinity does not constitute a health problem nowadays; however, mostly complex diseases affected 52.5 percent of offspring in consanguineous couples. The study lays the foundations to establish a health education and promotion strategy at the community level(AU)

Analysis of a patient with early-onset Parkinson’s disease and PARK7 gene variation / 中华医学遗传学杂志

Objective@#To explore the genetic basis of a patient with early-onset Parkinson disease from a consanguineous family.@*Methods@#Homozygosity mapping and Sanger sequencing of cDNA were used to identify the causative mutation.@*Results@#A homozygous missense variation (c.56C>G, p. Thr19Arg) in the PARK7 gene was identified in the patient. In silico analysis suggested the c. 56C>G variation to be pathogenic.@*Conclusion@#Homozygous c. 56C>G variation of the PARK7 gene was the disease-causing variation in this family.

Homozygosity mapping and mutation analysis of a consanguineous marriage family with autosomal recessive cerebellar ataxia / 中华神经科杂志

Objective To identify the pathogenic gene for a Chinese Han consanguineous marriage family with autosomal recessive cerebellar ataxia by homozygosity mapping and mutation analysis.Methods Six members of the family were enrolled in this study,including 3 patients,the unaffected sibling and their parents of first cousin marriage.After excluding GAA repeats mutation of FXN gene,whole-genome single nucleotide polymorphism (SNP) microarray scanning and homozygosity mapping were performed to localize the candidate gene.The coding regions and intronic flanking sequences of the candidate genes were analyzed.Results Four candidate regions were identified,including 2p25.3,9q22.2-34.3,13q12.3-14.3 and 17p13.The SETX gene localizing in 9q22.2-34.3 that is responsible for ataxia with oculomotor apraxia 2 was analyzed at first.There were 4 mutations in exon 10,including three missense mutations (c.3576T ＞ G,p.D1192E ; c.3754G ＞ A,p.G1252R; c.4156A ＞ G,p.I1386V) and a deletion mutation (c.5084_5087delAGTC,p.Q1695_S1696del).Three patients were homozygous of the 4 mutations,an unaffected sibling was normal,and their parents were heterozygous of 4 mutations.Conclusions The pathogenic haplotype comprising four mutations of the SETX gene was identified in the consanguinity family.c.5084_5087delAGTC (p.Q1695_S1696del) is a novel mutation.The affected individuals of this family were characterized by mild phenotype and slow progress without oculomotor apraxia,indicating the clinical variability of the disease.

A Novel Missense Mutation in SRD5A3 Causes Congenital Disorder of Glycosylation Type I (Cerebello-Ocular Syndrome)

Abstract A consanguineous Qatari family having an autosomal recessive disorder characterized by severe mental retardation, cerebellar vermis hypoplasia, retinal degeneration, optic nerve atrophy, ataxic gait, and seizures was studied for identification of the offending gene and mutation. Homozygosity mapping identified an 11.4 Mb critical interval at 4q12 to q13.2 that would contain the gene responsible for the disorder. Ten positional candidate genes were screened for pathogenic mutations, but none were identified. Next-generation exome sequencing in one affected individual identified a novel SRD5A3 missense mutation c.T744G/p.F248L, which was subsequently confirmed by Sanger sequencing, suggesting a congenital disorder of glycosylation type IQ defect. Isoelectric focusing of serum transferrin showed a type I pattern indicative of an .-glycan assembly defect. This is a novel pathogenic mutation and the first SRD5A3 missense mutation as all others are protein-truncating mutations.