Pei Chen Wu

Mosaic Trisomy 7 at Amniocentesis: Prenatal Diagnosis and Molecular Genetic Analyses

OBJECTIVE To present prenatal diagnosis and molecular genetic analyses of mosaic trisomy 7. MATERIALS, METHODS AND RESULTS A 38-year-old primigravid woman underwent amniocentesis at 19 weeks of gestation because of her advanced maternal age. Amniocentesis revealed a karyotype of 47,XY,+7[26]/46, XY[16]. Repeated amniocentesis at 21 weeks of gestation revealed a karyotype of 47,XY,+7[20]/46,XY[17]. Simultaneous cordocentesis revealed a karyotype of 46,XY in 100/100 cultured lymphocytes. Polymorphic DNA marker analyses of uncultured amniocytes and cord blood revealed a diallelic pattern with seemingly equal biparental inheritance of chromosome 7. Repeated cordocentesis and chorionic villus sampling at 23 weeks of gestation revealed a karyotype of 47,XY,+7[2]/46,XY[66] in cord blood and a karyotype of 47,XY,+7 in 24/24 cultured chorionic villi cells. Level II ultrasonography was normal. At 40 weeks of gestation, a 2,708 g normal male baby was delivered. The peripheral blood had a karyotype of 46,XY in 100/100 lymphocytes. Molecular analyses of placenta, urine, buccal swab, and peripheral blood revealed a diallelic pattern and seemingly equal biparental inheritance of chromosome 7 in all tissues. At 3 months of age, he manifested hypopigmented skin and inguinal hernia, but showed normal growth and mental development. Fluorescence in situ hybridization analysis of inguinal hernia sac tissue revealed that 19/100 (19%) of nuclei had three chromosome 7 signals. CONCLUSION Mosaic trisomy 7 at amniocentesis may be derived from a cell culture artifact from an undetected low level of trisomy 7 mosaicism in uncultured amniocytes, and can be associated with favorable fetal outcome if the blood has a normal karyotype or a very low level of mosaicism and if uniparental disomy for chromosome 7 is excluded.

A de novo 7.9 Mb deletion in 22q13.2→qter in a boy with autistic features, epilepsy, developmental delay, atopic dermatitis and abnormal immunological findings

We report a 5-year-old boy with mental retardation, autistic features, epilepsy, developmental delay, atopic dermatitis and abnormal immunological findings, carrying a 7.9 Mb de novo deletion of chromosome 22q13.2→qter. This region contains the SHANK3, NCAPH2 and CYP2D6 genes which are associated with T-cell immune response. The present case provides evidence that 22q13 deletion syndrome may be associated with immune system dysfunction in addition to neuropsychiatric disorders.

Unbalanced reciprocal translocations at amniocentesis

OBJECTIVE To present perinatal findings, modes of ascertainments, and modes of segregation in unbalanced reciprocal translocations detected at amniocentesis. MATERIALS AND METHODS Between January 1987 and July 2010, 40 cases with unbalanced reciprocal translocations were diagnosed by amniocentesis at Mackay Memorial Hospital, Taipei, Taiwan. The 40 cases originated from 29 families; 21 families with one case, 7 families with two cases, and 1 family with five cases. RESULTS Of 40 cases, 33 (82.5%) presented fetal ultrasound abnormalities and 7 (17.5%) presented no ultrasound abnormalities. Of 40 cases, 36 (90%) had a segregation mode of adjacent-1 2:2 segregation, 3 (7.5%) had a segregation mode of 3:1 segregation with tertiary trisomy, and 1 (2.5%) had a segregation mode of 3:1 segregation with tertiary monosomy. Of 29 families, 7 (24.1%) had de novo translocations and 22 (75.9%) had inherited translocations. In seven de novo cases, the main modes of ascertainments included abnormal ultrasound findings (n = 5) and advanced maternal age (n = 2). In 22 inherited families, the main modes of first ascertainment included abnormal ultrasound findings (n = 8), a previous aneuploid child (n = 8), advanced maternal age (n = 4), parental carrier status (n = 1), and abnormal maternal serum screening results (n = 1). Among 22 inherited families, 9 (40.9%) had a known parental carrier status, but 13 (59.1%) were unaware of parental carrier status at amniocentesis. CONCLUSION Unbalanced reciprocal translocations detected at amniocentesis are frequently associated with abnormal ultrasound findings. Prenatal diagnosis of an unbalanced translocation may incidentally detect a balanced translocation in the family. Prenatal diagnosis of fetal structural abnormalities should alert structural chromosome rearrangements and prompt cytogenetic analysis of the fetus and parents if necessary.

Array-CGH detection of a de novo 2.8 Mb deletion in 2q24.2-->q24.3 in a girl with autistic features and developmental delay.

We report a 3 years and 4 months old girl with autistic features, developmental delay, mental retardation, language impairment and dysmorphic features, carrying a 2.8 Mb de novo deletion of chromosome 2q24.2-->q24.3 detected by array-CGH. This region contains two neuronal voltage-gated sodium channel genes SCN2A and SCN3A.

Prenatal diagnosis and molecular cytogenetic characterization of de novo partial trisomy 7p (7p15.3→pter) and partial monosomy 13q (13q33.3→qter) associated with Dandy-Walker malformation, abnormal skull development and microcephaly.

OBJECTIVE To present the prenatal diagnosis and molecular cytogenetic characterization of de novo partial trisomy 7p (7p15.3→pter) and partial monosomy 13q (13q33.3→qter) associated with Dandy-Walker malformation (DWM), abnormal skull development, microcephaly and multiple congenital anomalies. MATERIALS, METHODS AND RESULTS A 42-year-old woman, gravida 6, para 1, was referred for amniocentesis at 18 weeks of gestation because of her advanced maternal age. Amniocentesis revealed an aberrant derivative chromosome 13, or der(13). The parental karyotypes were normal. Spectral karyotyping showed that the der(13) was derived from a translocation of chromosomes 7 and 13. Fluorescence in situ hybridization using subtelomeric probes revealed three signals of 7pTEL and only one signal of 13qTEL, indicating a translocation between 7p and 13q in the der(13). Array-based comparative genomic hybridization demonstrated partial trisomy 7p (7p15.3-p22.3) and partial monosomy 13q (13q33.3-q34). The karyotype was 46,XY,der(13)t(7;13)(p15.3;q33.3). Polymorphic DNA marker analysis revealed the paternal origin of the aberrant chromosome. Level II ultrasound at 24 weeks of gestation revealed microcephaly, an irregular-shaped skull, DWM, nuchal edema and transposition of the great arteries. CONCLUSION Spectral karyotyping, fluorescence in situ hybridization and array-based comparative genomic hybridization are useful for prenatal investigation of the nature of a de novo aberrant derivative chromosome. Partial trisomy 7p (7p15.3→pter) and partial monosomy 13q (13q33.3→qter) can be associated with DWM, microcephaly, abnormal skull development, nuchal edema and cardiovascular defects on prenatal ultrasound.

Prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome derived from chromosome 8.

OBJECTIVE To present prenatal diagnosis and molecular cytogenetic characterization of a small supernumerary marker chromosome (sSMC) derived from chromosome 8 by multiplex ligation-dependent probe amplification (MLPA), fluorescence in situ hybridization (FISH), spectral karyotyping (SKY) and array comparative genomic hybridization (aCGH). CASE REPORT A 42-year-old woman, gravida 6, para 3, underwent amniocentesis at 19 gestational weeks because of advanced maternal age. Amniocentesis revealed a de novo ring-shaped sSMC in all 13 colonies of the amniocytes. The karyotype was 47,XY,+mar. The MLPA showed duplications of 8p11.21-specific probes. At 24 gestational weeks, level II ultrasound revealed a left multicystic kidney in the fetus. Other internal organs were unremarkable. Repeat amniocentesis revealed a karyotype of 47,XY,+mar[25]/46,XY[2]. The sSMC was characterized by SKY and FISH, which showed a chromosome 8 origin of the sSMC. Oligonucleotide-based aCGH demonstrated a 4.4-Mb duplication of 8p11.21q11.1 [arr cgh 8p11.21q11.1 (42,637,263-47,062,180)×3]. The karyotype was 47,XY,+r(8) (p11.21q11.1)[25]/46,XY[2]. Polymorphic DNA marker analysis revealed no uniparental disomy for chromosome 8. The woman elected to continue the pregnancy and at 34 gestational weeks, a 1,820 g male baby without craniofacial dysmorphism was delivered. At the age of 1 month, the infant was apparently normal except for left multicystic kidney disease and mild ventriculomegaly. CONCLUSION MLPA, SKY and aCGH are helpful in genetic counseling of prenatally detected sSMCs by providing the immediate information on the origin and the genetic contents of the sSMC.

Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from ring chromosome 4

OBJECTIVE To present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from ring chromosome, or r(4) by spectral karyotyping (SKY), fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (aCGH). MATERIALS, METHODS, AND RESULTS A 37-year-old, primigravid woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a de novo ring-shaped sSMC in 16 of 31 amniocyte colonies. The parental karyotypes were normal. Level II ultrasound findings were unremarkable. Repeated amniocentesis revealed a karyotype of 47,XX,+mar[17]/46,XX[19]. The sSMC was characterized by SKY and FISH, which showed a chromosome 4 origin of the sSMC. aCGH demonstrated a 21.7-Mb gain in the gene dosage encompassing the region of 4p12→q13.2. The sSMC was r(4)(p12q13.2). The fetal karyotype was 47,XX,+r(4)(p12q13.2)[17]/46,XX[19]. The pregnancy was subsequently terminated. The fetus postnatally manifested hypertelorism, epicanthic folds, a prominent nose, a triangular face, low-set ears, clinodactyly of the fingers, and small big toes. Postnatal cytogenetic analyses of fetal and extraembryonic tissues revealed the karyotypes of 47,XX,+r(4)[18]/46,XX[21] in cord blood, 47,XX,+r(4)[20]/48,XX,+r(4),+r(4)[1]/46,XX[9] in umbilical cord, 47,XX,+r(4)[14]/47,XX,+dic r(4)[1]/46,XX[25] in skin, 47,XX,+r(4)[15]/46,XX[25] in amnion, and 47,XX,+r(4)[12]/47,XX,+dic r(4)[1]/46,XX[2] in placenta. CONCLUSION SKY, FISH, and aCGH are helpful in genetic counseling of prenatally detected sSMCs by providing the immediate and thorough information on the origin and genetic component of the sSMC.

Inv dup del(9p): Prenatal diagnosis and molecular cytogenetic characterization by fluorescence in situ hybridization and array comparative genomic hybridization

OBJECTIVE To present molecular cytogenetic characterization of prenatally detected inverted duplication and deletion of 9p, or inv dup del(9p). MATERIALS, METHODS, AND RESULTS A 35-year-old primigravid woman underwent amniocentesis at 16 weeks of gestation because of advanced maternal age. Amniocentesis revealed a derivative chromosome 9, or der(9) with additional material at the end of the short arm of one chromosome 9. Parental karyotypes were normal. Level II ultrasound showed ventriculomegaly and normal male external genitalia. Repeated amniocentesis was performed at 20 weeks of gestation. Array comparative genomic hybridization revealed a 0.70-Mb deletion at 9p24.3 and an 18.36-Mb duplication from 9p24.3 to 9p22.1. The distal 9p deletion encompassed the genes of DOCK8, ANKRD15, FOXD4, DMRT1, and DMRT3. Fluorescence in situ hybridization analysis using bacterial artificial chromosome clone probes specific for 9p confirmed that the der(9) was derived from the inv dup del(9p). The karyotype of the fetus was 46,XY,inv dup del(9)(:p22.1-->p24.3::p24.3-->qter)dn or 46,XY,der(9) del(9)(p24.3) inv dup(9)(p22.1p24.3)dn. Polymorphic DNA marker analysis determined a maternal origin of the inv dup del(9p). A 512-g male fetus was subsequently terminated at 22 weeks of gestation with facial dysmorphism. The fetus had normal male external genitalia without sex reversal. CONCLUSION Fluorescence in situ hybridization and array comparative genomic hybridization are useful to determine the nature of a prenatally detected aberrant chromosome derived from the inv dup del. Male fetuses with inv dup del(9p) and haploinsufficiency of DMRT1 and DMRT3 may present normal male external genitalia without sex reversal.

Short rib-polydactyly syndrome type II (Majewski): Prenatal diagnosis, perinatal imaging findings and molecular analysis of the NEK1 gene

OBJECTIVE To demonstrate perinatal imaging findings and to investigate the mutation in the NEK1 gene in a fetus with type II short rib-polydactyly syndrome (SRPS) (Majewski). CASE REPORT A 34-year-old woman with a past history of fetal SRPS was referred to the hospital at 16 weeks of gestation because of sonographic diagnosis of short limbs in the fetus. Fetal ultrasound revealed short ribs, short limbs, absence of tibiae, polydactyly, syndactyly and choroid plexus cysts. At 21 weeks of gestation, polycystic kidneys were found. The pregnancy was terminated, and a fetus was delivered with facial dysmorphism, a median cleft lip, a narrow chest, micromelia, aplasia of tibiae, hypoplastic nails, syndactyly and postaxial polydactyly. The karyotype was 46,XX. Molecular analysis of fetal tissues showed a paternal-origin heterozygous splice site mutation in intron 7 (c.465-1 G>A) in the NEK1 gene, but no mutations in the genes of WDR35, DYNC2H1, IFT80, EVC and EVC2. The NEK1 mutation causes an alteration of the splice acceptor site of intron 7 (IVS7-1 G>A). No second mutation was identified. CONCLUSION Tibial aplasia, choroid plexus cysts and polycystic kidneys can be prominent prenatal ultrasound findings of type II SRPS. The present case provides evidence for a correlation of NEK1 mutation with type II SRPS.

De novo duplication of Xq22.1→q24 with a disruption of the NXF gene cluster in a mentally retarded woman with short stature and premature ovarian failure

OBJECTIVE To present molecular cytogenetic characterization of a de novo duplication of Xq22.1→q24 in a mentally retarded woman with short stature and premature ovarian failure. MATERIALS AND METHODS A 19-year-old woman presented with psychomotor retardation, developmental delay, mental retardation, short stature, low body weight, general muscle hypotonia, distal muscle hypotrophy of the lower extremities, elongated digits, scanty pubic and axillary hair, hypoplastic external female genitalia, and secondary amenorrhea but no clinical features of Pelizaeus-Merzbacher disease. Conventional cytogenetic analysis revealed a karyotype of 46,X,dup(X)(q22.1q24). Fluorescence in situ hybridization determined a direct duplication with a linear tandem orientation. Array comparative genomic hybridization demonstrated partial trisomy Xq [arr cgh Xq22.1q24 (101,490,234-119,070,188 bp)×3] with a 17.6-Mb duplication. RESULTS The duplicated region contained NXF2B, NXF4, NXF3, PLP1, and PGRMC1 genes. There was a disruption of the NXF gene cluster of Xcen-NXF5-NXF2-NXF2B-NXF4-NXF3-Xqter. CONCLUSION A duplication of Xq22.1→q24 with a disruption of the NXF gene cluster in female patients can be associated with clinical manifestations of mental retardation in addition to short stature and premature ovarian failure.