Gene-deletion and carrier detections, and prenatal diagnosis of Duchenne muscular dystrophy by analysis of the dystrophin gene amplified by polymerase chain reaction.

Polymerase chain reaction (PCR)-based diagnosis was carried out in 62 patients (57 probands) with Duchenne or Becker muscular dystrophy (DMD or BMD) and 226 members in 57 families. The PCR studies were also performed for carrier detection in 57 mothers and 58 sisters, and prenatal diagnosis of 4 fetuses at risk of DMD. The PCR with 7 sets of primers, which amplify 7 different exon-sequences of the dystrophin gene, detected gene deletion of at least one exon in 49% of the probands. The PCR with the other 4 primer sets, which amplify 3 intragenic loci, and subsequent endonuclease digestion detected in 84% of the mothers a heterozygous pattern in at least one such locus/segment. Using the same primer sets, carrier detection was successful in 5 sisters of familial DMD cases, while recombination between the ERT87 and the 3' end intragenic loci was observed in 11% of family members studied. Prenatal diagnosis was made in all the 4 fetuses; two males were affected, one male fetus non-affected, and the remaining one female fetus a carrier. Thus, the PCR study and the primers used in the present study are useful and convincing for rapid diagnosis of DMD and/or BMD.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

应用多重PCR和MLPA技术检测DMD患者和携带者的基因突变及产前诊断

目的 应用多重PCR和多重连接依赖探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术检测Duchenne/Becker肌营养不良症(Duchenne/Becker muscular dystrophy,DMD/BMD)患者、携带者并应用于产前诊断.方法 首先采用多重PCR对临床诊断为DMD/BMD的患者检测DMD基因的26个外显子,未查到缺失突变者和可能的携带者采用MLPA检测全部79个外显子是否有缺失或重复突变.对产前诊断病例,用PCR法检测缺失突变,用MLPA法检测重复突变.结果 多重PCR对22例患者的DMD基因的26个外显子检测.13例有缺失突变.未查到常见缺失突变的9例患者经MLPA检测DMD基因的全部79个外显子,3例为重复突变、1例为单个第18外显子缺失、其他5例未查到缺失和重复突变.16例携带者中,3例有家族史,其中2例检出突变;13例为检测到突变的散发病例患儿的母亲,有8例检测到突变.产前诊断9个胎儿(其中双胎1例),2例胎儿有突变,引产后核实无误;7例胎儿未检测到突变,现均已分娩.结论 多重PCR可检出92.86%的缺失突变并可用于缺失突变的产前诊断,因其简便、可靠、价廉可作为临床上DMD/BMD基因诊断的初选.MLPA可用于多重PCR未检测到缺失突变的患者及携带者的检查.     

Mutation analysis and prenatal diagnosis for 50 pedigrees affected with Duchenne/Becker muscular dystrophyCSCD

Objective To establish individualized prenatal diagnosis program for families affected with Duchenne/Becker muscular dystrophy (DMD/BMD) and different clinical background using a variety of methods. Methods Multiplex ligation-dependent probe amplification (MLPA) was performed on 50 patients suspected for DMD/BMD. For single exon deletions of the DMD gene, PCR was used for validating the results. For those without any deletion or duplication, Sanger sequencing was used to screen for DMD gene mutations in the children and their mothers. Prenatal genetic testing was provided to female carriers using chorionic villus, amniocentesis or cord blood samples. To ensure the accuracy of diagnosis, all prenatal specimens were also subjected to linkage analysis. Results Among the 50 patients with DMD/ BMD, 23 harbored large deletions, 11 only had single exon deletions, 10 harbored duplications, and 5 had small scare mutations. No mutation was detected in one family. For 37 women undergoing prenatal diagnosis, 10 fetuses were identified as affected males, 6 were female carriers, while 21 were not found to carry any mutation. Testing of creatine kinase was consistent with the results of prenatal diagnosis. For a patient harboring exon 51 deletion, the same mutation was found in a fetus but not in their mother. The proband and fetus had inherited the same haplotype, which suggested that the mother probably has germline mosaicism for the mutation. Conclusion Application of individualized methods for analyzing pregnant women with different clinical background can minimize the risk for giving birth to further children affected with DMD/BMD. © 2018 West China University of Medical Sciences. All rights reserved.     

Possibilities and limitation of prenatal diagnosis and carrier determination for Duchenne and Becker muscular dystrophy using cDNA probes.

Two cDNA probes, cf23a and cf56a, identify deletions of selected exons in about 50% of our DMD/BMD patients. We have estimated the most likely order of the 11 exons detectable with both probes with respect to the different extensions of the deletions. In one of our BMD pedigrees, the observed deletion could be traced in the affected males through three generations. This result shows that with the use of cDNA probes detecting deletions, the only risk of error in genomic prenatal diagnosis is the general high frequency of new mutations for DMD/BMD. This is important progress in diagnosis compared to the 2 to 5% risk of misdiagnosis because of crossing over events using conventional linkage analysis with bridging or intragenic probes. The first prenatal diagnosis of an unaffected fetus of a woman who is a DMD carrier according to ultrasound examination is described. In one of our DMD males, the cDNA probe cf56a detects a deletion breakpoint. His sister also shows the altered band and is therefore a DMD carrier, while his mother has a totally normal band pattern. The interpretation of this observation could be either germline mosaicism or two identical new mutations. The identification of deletion breakpoints is a new diagnostic strategy, especially for carrier determination, which excludes misdiagnosis owing to crossing over events and the problems of dosage estimation. It is, however, limited by the low frequency of breakpoints detectable with cDNA probes. Therefore, the generation of new intron probes in this region is an important goal.     

Allele frequencies of intragenic,and 5′ and 3′ markers of the dystrophin gene in Japanese families afflicted with Duchenne or Becker muscular dystrophy

Summary Using the polymerase chain reaction method (PCR), we examined the allele frequencies and heterozygosities of 7 polymorphic sites (pERT87, and CA polymorphisms in the 5 and 3 regions) of the dystrophin gene in 20 Japanese Duchenne muscular dystrophy and Becker muscular dystrophy (DMD or BMD) families consisting of 36 males, including 23 cases of DMD and BMD, and 28 females. The allele frequencies of three primer and enzyme sets in the pERT87 locus were well comparable to those in the previously reported Japanese female cases but different from in other countries. The frequencies of 5 markers of the dystrophin gene in Japanese were different from the reported Caucasian frequencies. As for 5DYS-I and 5DYS-II, the numbers of alleles in our cases were less than in Caucasians, and the heterozygosities of all three markers (5DYS-I, II and III) were lower than in Caucasians. However, the 3CA polymorphisms showed almost the same frequencies and heterozygosities as in Caucasians. All of our females showed a heterozygous pattern for at least one locus, with the combination of the seven markers. The usefulness of linkage analysis involving PCR methods with these intragenic, and 5 and 3 markers of the dystrophin gene in the carrier and prenatal diagnosis of DMD and BMD was confirmed by the successful prenatal diagnoses in 15 fetuses, the exception being one case considered to have a new mutation.     

应用荧光原位杂交技术诊断基因缺失型进行性假肥大性肌营养不良携带者

目的 建立应用荧光原位杂交(fluorescent in situ hybridization，FISH)方法检查进行性假肥大性肌营养不良(Duchenne／Becker muscular dystrophy，DMD／BMD))患者家系中女性亲属是否为携带者的方法。方法 采用多重聚合酶链反应对19例DMD／BMI)先证者进行基因诊断，从中筛选出两例缺失dystrophin基因外显子46的患者，其中l例有阳性家族史，另l例为散发病例，采用双色FISH对其女性亲属进行携带者的检查。结果 在有阳性家族史的1例患者的家系中检出4例携带者；在另一散发病例的家系中检出1例所缺失基因片段的体细胞嵌合体。结论 与多重PCR相结合，应用双色FISH检出基因缺失型DMD／BMD携带者是一个切实可行的诊断方法，对于所缺失基因片段的体细胞嵌合体的诊断是FISH方法的一个突出的优点，这对DMD／BMD家系的遗传咨询以及产前诊断指征的确立具有重要意义。     

假肥大型肌营养不良症基因诊断及遗传分析

目的对假肥大型肌营养不良症（DMD／BMD）患者进行基因诊断并对家系进行遗传分析,以提高对DMD／BMD的基因诊断水平及有效的遗传咨询。方法对40例DMD／BMD患者应用18对引物多重PCR技术进行Dystrophin基因缺失诊断,收集完整家系资料进行遗传分析以判断致病基因携带者及评估风险。结果40例DMD／BMD患者基因诊断有27例至少存在一个外显子片段缺失（67．5％）,13例未检测到缺失（32．5％）。通过对家系的遗传分析判断出致病基因携带者。结论多重PCR作为一种简便快速的诊断方法可对DMD／BMD患者进行基因诊断;对风险家系进行遗传分析、判断致病基因携带者以进行有效的遗传咨询,进而控制遗传病。     

产前胎儿性别PCR鉴定方法及其在X连锁遗传病诊断中的应用

作者采用ＰＣＲ技术扩增Ｙ染色体长臂上的ＤＹＺ－１基因，对２２８例羊水进行了产前胎儿性别鉴定，其中４例为ＤＭＤ／ＢＭＤ的高危患儿，１例为甲型血友病的高危患儿。同时用常规细胞遗传学检查作比较，结果表明ＰＣＲ技术用于产前胎儿性别鉴定具有快速、简便、灵敏、特异性强、方法稳定可靠等优点，对Ｘ连锁遗传病的产前诊断具有重要作用。     

Two non-contiguous duplications in the DMD gene in a Spanish family

DMD and BMD are X-linked myopathy diseases in most cases caused by intragenic deletions, but duplications also appear in a significant number of cases. We present a complex duplication pattern detected by MLPA, a recently formulated method applied here to amplify the 79 exons of the DMD gene. We found a double-duplication in two DMD-affected brothers and in their carrier mother, which consist of two non-contiguous duplications encompassing exons 2 to 7 and exons 50 to 55. Different models are presented to explain formation of this genetic variant.     

Two Non-Contiguous Duplications in the DMD Gene in a Spanish Family

DMD and BMD are X-linked myopathy diseases in most cases caused by intragenic deletions, but duplications also appear in a significant number of cases. We present a complex duplication pattern detected by MLPA, a recently formulated method applied here to amplify the 79 exons of the DMD gene. We found a double-duplication in two DMD-affected brothers and in their carrier mother, which consist of two non-contiguous duplications encompassing exons 2 to 7 and exons 50 to 55. Different models are presented to explain formation of this genetic variant.