A paternally derived inverted duplication of 7q with evidence of a telomeric deletion

We report on a de nova constitutional rearrangement involving the long arm of chromosome 7 in a second trimester fetus with the karyotype of 46,XX, inv dup del (7)(pter-q36::q36-q21.2:) pat. Both a large duplication (q21.2-q36) and a small deletion (within q36) were confirmed by FISH studies. DNA analysis on the family showed that the abnormal chromosome was derived from a single paternal homolog. A mechanism is proposed in light of this finding. The phenotype at autopsy was consistent with reported cases of similar duplications in chromosome 7 in that hydrocephalus, a depressed nasal bridge, low set ears, microretrognathia and a short neck were present. Am. J. Med Genet. 68:76–81, 1997 © 1997 Wiley-Liss, Inc.     

一例8P倒位重复伴末端缺失综合征的细胞和分子遗传学研究

目的 明确1例智力低下患儿8号染色体短臂异常的片段来源和位置,探讨该异常核型的发生机制、临床表型特征和家庭再发风险.方法 高分辨显带分析患者及其父母外周血染色体核型,比较基因组杂交芯片(array comparative genomic hybridization,array CGH)精细定位拷贝数异常改变的染色体片段区域,荧光定量PCR验证芯片分析结果.结果 患儿异常染色体为8p11.2-p23.1倒位重复和8p23.2-pter缺失;在重复和缺失之间间隔有1个长为5.70 Mb的拷贝数正常片段,嗅觉受体(olfactory receptor,OR)基因簇位于该片段的两端.结论 这是1例典型的inv dup del(8p)综合征,临床上以重度智力低下、大脑发育不良和特殊面容为主要特征,由8p23.1上OR基因簇的重复序列发生非等位同源重组所致.再生育时,不仅要预防inv dup del(8p)的再发风险,还要注意由同一重组机制造成的另外3种不良结局的妊娠风险.就目前所知,这是国内第1例明确诊断的inv dup del(8p)综合征.     

Trisomy 20p resulting from inverted duplication and neocentromere formation

Normal human centromeres contain large tandem arrays of α-satellite DNA of varying composition and complexity. However, a new class of mitotically stable marker chromosomes which contain neocentromeres formed from genomic regions previously devoid of centromere activity was described recently. These neocentromeres are fully functional yet lack the repeat sequences traditionally associated with normal centromere function. We report here a supernumerary marker chromosome derived from the short arm of chromosome 20 in a patient with manifestations of dup(20p) syndrome. Detailed cytogenetic, FISH, and polymorphic microsatellite analyses indicate the de novo formation of the marker chromosome during meiosis or early postzygotically, involving an initial chromosome breakage at 20p11.2, followed by an inverted duplication of the distal 20p segment due to rejoining of sister chromatids and the activation of a neocentromere within 20p12. This inv dup(20p) marker chromosome lacks detectable centromeric α-satellite and pericentric satellite III sequences, or centromere protein CENP-B. Functional activity of the neocentromere is evidenced by its association with 5 different, functionally critical centromere proteins: CENP-A, CENP-C, CENP-E, CENP-F, and INCENP. Formation of a neocentromere on human chromosome 20 has not been reported previously and in this context represents a new mechanism for the origin of dup(20p) syndrome. Am. J. Med. Genet. 85:403–408, 1999. © 1999 Wiley-Liss, Inc.     

Four new cases of inverted terminal duplication: A modified hypothesis of mechanism of origin

We present 4 recently diagnosed cases of inverted tandem duplication with involvement of the respective terminal band. Based on these 4 cases and review of the literature, the term “inverted terminal duplication” is proposed to designate specifically the type of inverted tandem duplication which involves the terminal band. A modification of the previous hypothesis of mechanism of origin is advanced. It is speculated further that a telomeric deletion of a meiotic chromosome followed by a U-type reunion of the chromatids, considered to be the first steps of the proposed mechanism of origin, may not be a rare gonadal event. © 1995 Wiley-Liss, Inc.     

Structural abnormalities of chromosome 8 and fetoplacental discrepancy: A second case report and review of fetal phenotype of 8p inverted duplication deletion syndrome

We described a new second case of fetoplacental discrepancy involving first trimester prenatal detection of mosaic isochromosome i (8) (q10). A 32-year-old woman underwent chorionic villous sampling because of increased fetal nuchal translucency. Analysis of direct chromosome preparations was performed by R-banding and FISH using subtelomeric, centromeric and whole chromosome painting probes for chromosome 8 showing the presence of an isochromosome 8q with a complex, female mosaic karyotype: mos 46,XX,i (8) (q10)[13]/46,XX,del (8) (p23)[10]. Cytogenetic analysis of cultured CVS showed an interstitial duplication with concomitant terminal deletion of the short arm of chromosome 8: 46,XX,der (8)del (8) (p23)dup (8) (p?)[18]. Array-CGH analysis from cultured trophoblasts and fetal tissues revealed a 6.69 Mb terminal deletion in 8p23.3p23.1 associated with a 31.49 Mb duplication in 8p23.1p11.1. FISH analysis confirmed the 8p inverted duplication deletion syndrome. Moreover, polymorphic DNA marker analysis demonstrated that the derivative chromosome 8 was of maternal origin. FISH analysis of cultured peripheral blood lymphocytes showed that the mother also carried a cryptic paracentric inversion inv (8) (p23). Our report contributes to expand the fetal phenotype of 8p inverted duplication deletion syndrome and also provides further insight into the underlying mechanism of this rare genomic disorder.     

Inverted duplication of 8p: Ten new patients and review of the literature

We evaluated 10 patients with an inverted tandem duplication of 8p. Inverted duplications of chromosome 8 have been reported infrequently, and no syndrome has been previously identified. All 8 patients on whom birth histories were available were hypotonic at birth, and had feeding difficulties in the neonatal period. All patients have significant developmental delay. Manifestaions present in 5 or more patients were prominent forehead, high arched palate, large mouth with a thin upper lip, malformed and/or apparently lowset ears, broad nasal bridge, dental and skeletal abnormalities, and joint laxity or hyperextensibility. Variation in the phenotype may, in part, be explained by the different breakpoints. Recurrence risks of de novo rearrangements are probably very low, but for the recombinants the risk may be significant. The duplication appeared to be de novo in 6 patients (both parental karyotypes were normal); maternal karyotypes were normal in 2 patients, and both parrents of 1 patient were not available. One propositus had a monocentric recombinant of a paracentric inv(8) (p12p23.3) carried by the mother, and is one of only 6 known cases of duplication associated with a balanced paracentric inversion in a parent. The carrier parent was the mother in 5 of those 6 cases. Each case involved a different chromosome, and each probably was created by an unusual meiotic recombination event. Inverted duplication 8p is one of the most common duplications observed in our laboratories, and ranks in frequency with the classical deletions, such as Wolf-Hirschhorn and cri-du-chat syndromes and duplication or secondary trisomy 15ql. Since 1/7 cases with complete parental karyotypes was associated with a familial rearrangement, parental karyotype studies should be considered in all cases of tandem duplication. © 1993 Wiley-Liss, Inc.     

Protelomeric sequences are deleted in cases of short arm inverted duplication of chromosome 8

We present a patient with a de novo inverted duplication of the short arm of chromosome 8. Molecular analysis confirmed the cytogenetic suspicion of a simultaneous deletion of the tip of the short arm and indicated the maternal origin of the abnormality. This deletion made no detectable contribution to the phenotype of the patient which was comparable to that of previous cases of 8p duplication. Similar investigations of inverted duplications involving other chromosomes may reveal unexpected deletions with significant phenotypic consequences. © 1994 Wiley-Liss, Inc.     

Inversion duplication of the short arm of chromosome 8: Clinical data on seven patients and review of the literature

We report on clinical and cytogenetic data on 5 children and 2 adults with a de novo inverted duplication of the short arm of chromosome 8, and we give a review of 26 patients from the literature. The clinical picture in young children is characterized by minor facial anomalies, hypotonia, and severe developmental delay. In older patients the facial traits are less characteristic, spastic paraplegia develops, and severe orthopedic problems are frequent. Psychomotor retardation is always severe-to-profound. Duplication of 8p21-p22 results in a clinically recognizable multiple congenital anomalies/mental retardation (MCA/MR) syndrome. It is shown that in all patients examined, the duplication was accompained by a deletion of the most terminal part of 8p. © 1995 Wiley-Liss, Inc.     

Clinical and cytogenetic findings in seven cases of inverted duplication of 8p with evidence of a telomeric deletion using fluorescence in situ hybridization

We report on the clinical and cytogenetic findings in 7 cases of inverted duplication of region 8p11.2-p23. The phenotype of inv dup (8p) compiled from this series and the literature (N = 29) consists of severe mental retardation (100%), minor facial alterations (97%), agenesis of the corpus callosum (80%), hypotonia (66%), orthopedic abnormalities (58%), scoliosis/kyphosis (40%), and congenital heart defect (26%). A telomeric deletion of region 8p23.3-pter was confirmed in 3 of our cases studied using fluorescent in situ hybridization with a telomeric probe for 8p. Thus, these karyotypes are inv dup del(8) (qter→p23.1::p23.1→p11.2:). Our findings sugest that most cases of inv dup(8p) probably have a telomeric deletion. © 1995 Wiley-Liss, Inc.     

Neuroblastoma in a pediatric patient with a microduplication of 2p involving the MYCN locus

Neuroblastoma is the most common solid tumor of infancy, and mutations in several genes have been implicated as playing a role in tumor development. Here, we describe a pediatric patient with a constitutional microduplication of 2p24.3 who developed Stage 4 neuroblastoma at age 11 months. He represents the sixth patient described in the literature with partial trisomy 2p and neuroblastoma. All previous cases had duplication events spanning two genes implicated in neuroblastoma, MYCN and ALK. Our patient is unique because his duplicated region includes the MYCN gene only; the ALK gene is unaffected. These data, combined with the relatively high incidence of neuroblastoma reported in partial trisomy 2p patients, support the notion that MYCN duplication should be added to the growing list of genetic factors associated with an increased risk of neuroblastoma. The mechanism of increased risk is unclear, but the fact that our patient had dramatic amplification of MYCN in his tumor suggests that a germline duplication might predispose to further amplification. Additionally, our patient has several morphologic features common to patients with partial trisomy 2p including high forehead, hypertelorism, postaxial polydactyly, and developmental delay despite having a microduplication spanning approximately 1 Mb and including just three intact genes. This case may therefore help further delineate the genotype–phenotype correlations associated with partial trisomy 2p. © 2013 Wiley Periodicals, Inc.     

Duplication and deletion of chromosome band 2(p21p22) resulting from a familial interstitial insertion (2;11)(p21;p15)

Routine amniocentesis for advanced maternal age led to the prenatal diagnosis of a fetus with a karyotype of a 46,XX,del(2)(p21p22). At delivery the baby had holoprosencephaly as the major clinical finding, which has been associated with a deletion of band 2p21 in several other case reports. Chromosome studies of the parents showed a normal 46,XY karyotype in the father, and a balanced interstitial insertion 46,XX dir ins (11;2)(p15.1;p21p22) in the mother. Subsequent chromosome studies of other relatives documented a 23-year-old half-brother of the proposita with a partial trisomy for the segment deleted in the proposita. The half-brother showed the derivative chromosome 11 from the mother, resulting in a 46,XY,der(11)dup(2)(p21p22) karyotype. Major clinical findings include short stature, mild development delay, and behavior abnormalities. A half-sister of the proposita is also a balanced carrier of the dir ins (11;2) (p15.1;p21p22.2). The association of the deletion chromosome band 2p21 and the clinical finding of holoprosencephaly is further supported by the findings in this family. © 1994 Wiley-Liss, Inc.     

Small terminal deletion of 1p and duplication of 1q: Cytogenetics,FISH studies,and clinical observations at newborn and at age 16 years

A small, extra chromosome segment added to 1p was found by Q-banding 16 years ago in a newborn baby with low birth weight, short stature, wide open fontanelle, small palpebral fissures, depressed nose bridge, and inguinal hernia. This chromosome abnormality has been characterized recently with G-banding and fluorescence in situ hybridization using multiple DNA probes. The karyotype is now described as 46,XY, der(1)(qter→p36.13::q42.3→qter), representing a small deletion of 1p36.13-pter and a small duplication of 1q42.3-qter. Re-examination of this patient at age 16 years showed marked psychomotor delay, severely accentuated dorsal kyphosis and scoliosis, pectus excavatum, and other anomalies but no clinical signs of neuroblastoma. Comparison of the clinical findings in this case with those described in the patients having either a deletion of 1p36-pter or a duplication of 1q42-qter further illustrated the complexity of the genotype-phenotype relationship. Am. J. Med. Genet. 86:118–123, 1999. © 1999 Wiley-Liss, Inc.     

Deletion and duplication of 11p13-11p14: reciprocal aberrations derived from a paternal insertion

More than 100 cases of deletions that span 11p13-11p14 resulting in WAGR syndrome have been reported in the literature. In contrast, reports of duplications spanning this region are extremely rare. We here report on a deletion of 11p13-11p14 identified in a neonate with severe congenital anomalies including genitourinary abnormalities and aniridia, and the reciprocal duplication identified in his healthy older sibling. Both were derived from a paternal balanced insertion of the 11p region into 18q. The deletion and duplication were characterized by G-banding, FISH and array CGH, and are estimated to include approximately 5.5-5.8 Mb. This single family report highlights the mild phenotypes that can be associated with duplications of chromosomal regions, even those that are larger than 5 Mb and harbor known disease-related genes, and highlights the impact of identifying balanced carrier status in a parent for accurate genetic counseling.     

De novo inverted tandem duplication of the short arm of chromosome 12 in a patient with microblepharon

We present a patient with a de novo inverted duplication of nearly the entire short arm of chromosome 12 [inv dup(12)(p13.3p12)], which was characterized using GTG‐banding and spectral karyotyping. The patient was noted to have microblepharon, which has not been previously described in children with a similar chromosomal rearrangement. This patient represents one of the few examples of complete and pure trisomy 12p due to inverted duplication of the short arm of chromosome 12 and expands the clinical spectrum. © 2001 Wiley‐Liss, Inc.     

FAM35A/SHLD2/RINN2: A novel determinant of double strand break repair pathway choice and genome stability in cancer

FAM35A, alternatively known as SHLD2 and RINN2, was recently characterized as a DNA repair gene, evolutionarily conserved in higher vertebrates. FAM35A is a 53BP1-pathway factor and a component of the Shieldin/RINN complex. Among 53BP1-pathway factors, FAM35A has unique domains: an N-terminal disordered domain and three C-terminal OB-fold domains. These C-terminal domains have homology with the OB-fold domains of the single-stranded DNA binding protein, RPA1. With other 53BP1-pathway factors, FAM35A inhibits DNA end resection. FAM35A defective cell lines are sensitive to DNA double-strand break inducing agents. Concurrent FAM35A and BRCA1 defects in mammalian cell lines cause resistance to PARP inhibitors and camptothecin. The clinical relevance of this interaction is still unknown, but cancer genomics databases indicate that FAM35A is deleted in 6–13% of prostate cancers and in at least one triple negative breast cancer patient-derived BRCA1 defective cell line. From meta-analysis, FAM35A overexpression in patients with triple negative and basal-like breast cancers is associated with poor survival compared to patients with low expression. From this evidence, clarification of FAM35A's function and the related mechanism of chemoresistance is likely to have clinical implications.