Direct intrachromosomal duplication of 16q and heritable fragile site fra (10) (q25) in the same patient

Novel duplication on chromosome 16 (q12.1-q21) associated with behavioral disorder, mild cognitive impairment, speech delay, and dysmorphic features: case report

We report on the 10-year follow-up and clinical, cytogenetic, and molecular investigation of a girl admitted for evaluation because of speech delay, learning difficulties, aggressive behavior, and dysmorphic facial features that included high forehead, round face, epicanthic folds, low-set dysplastic ears, flat nasal bridge, long flat philtrum, thin upper lip, small mouth, and short neck. The analysis of high-resolution GTG- and CTG-banding chromosomes suggested a de novo direct duplication of 16q12-q21 region and fluorescence in situ hybridization analysis with whole-chromosome specific 16 probe confirmed that the duplicated genetic material originated from the chromosome 16. Subsequently, array-based comparative genomic hybridization analysis with a ≈ 75 kb resolution showed a 9.92 Mb gain on the long arm of chromosome 16 at bands q12.1 through q21. To the best of our knowledge, this is the first case of duplication 16q12.1q21 described in literature. Several genes within the duplicated region are possibly correlated with clinical features present in our patient. Clinical and cytogenetic findings were compared with the small number of reported patients with pure duplications 16q, partially overlapping the one in our patient. Clinical phenotype seems to be distinctive between the proximal-intermediate and intermediate-distal regions of the long arm of the chromosome 16. In particular, we observed a set of dysmorphic features that could present a characteristic dup 16q11.2-q13 phenotype. The present study illustrates the advantages of an integrative approach using both conventional and molecular techniques for the precise characterization and genotype-phenotype correlation in patients with dysmorphism, behavioral problems, and learning difficulties.

Investigation of a patient with a partial trisomy 16q including the fat mass and obesity associated gene (FTO): fine mapping and FTO gene expression study

A female patient with a partial trisomy 16q was described previously. Her clinical characteristics included obesity, severe anisomastia, moderate to severe mental retardation, attention deficit hyperactivity disorder, dysmorphic facies, and contractions of the small joints. In this article, we describe a more detailed analysis of the genetic anomaly in this patient. We were particularly interested in the involvement of the fat mass and obesity associated gene (FTO) in her duplication. Single nucleotide polymorphisms in FTO have been associated with obesity. The breakpoints of the duplication were precisely mapped using high-resolution oligonucleotide array comparative genomic hybridization (CGH). We found that the duplication spans 11.45 Mb on 16q11.2 to 16q13 and it includes FTO. The increased copy number of FTO was confirmed with a qPCR on genomic DNA of the patient. We investigated the influence of the increased FTO copy number on FTO gene expression in immortalized lymphocytes from the patient using qPCR. No evidence of increased FTO expression was detected in the patient's lymphocytes. We discuss these findings and we review clinical findings in patients with overlapping 16q duplications to determine the relationship between increased FTO copy number and obesity. Our review suggests that duplication of the FTO gene does not necessarily result in obesity.

A new small supernumerary marker chromosome, generating mosaic pure trisomy 16q11.1-q12.1 in a healthy man

Here we report on a healthy and fertile 30 years old man, who was carrier of a small supernumerary marker chromosome (sSMC). The application of molecular techniques such as fluorescence in situ hybridisation (FISH), microdissection and reverse painting, helped to characterize the sSMC which resulted to be derived from chromosome 16. In fact, the presence of euchromatin material from the long arm (16q) in the sSMC was demonstrated, and the karyotype can be written as mos 47, XY,+min(16)(:p11.1->q12.1:)[20]/46, XY [10].

Duplications of proximal 16q flanked by heterochromatin are not euchromatic variants and show no evidence of heterochromatic position effect

Extra euchromatic material was found within the major heterochromatic block of chromosome 16 (16qh) in one de novo case and seven members of two families. In contrast to the euchromatic variants of chromosome 9 (9qh), which are derived from pericentromeric euchromatin, molecular cytogenetics confirmed that these duplications were of 16q11.2-->q12.2 in the de novo case, of 16q11.2-->q13 in three members of family 1 and 16q11.2-->q12.1 in four members of family 2. The duplication had arisen as a post-zygotic mitotic event in the mother of family 1 and been transmitted paternally in family 2. An insertional mechanism of origin is proposed for the duplications in case 1 and family 1. Expression at the 16q13 matrix metalloproteinase-2 (MMP2)locus in families 1 and 2 was proportional to genomic copy number and not therefore consistent with position effect silencing due to the flanking blocks of heterochromatin. We conclude that proximal 16q duplications within 16qh are not novel euchromatic variants but associated with a variable phenotype including developmental delay, speech delay, learning difficulties and behavioural problems. The behavioural problems in families ascertained through affected children are much less severe than those encountered in previous patients ascertained as adults.

Prenatal diagnosis and molecular cytogenetic characterisation of a small de novo interstitial duplication 16q11.2-q13

We describe the first prenatally detected case of a small de novo interstitial duplication of chromosome 16q. This chromosomal aberration is extremely rare. Amniocentesis was indicated by advanced maternal age only. Ultrasound examinations of the foetus showed no abnormalities. Conventional and molecular cytogenetic analyses on cultured amniocytes by comparative genomic hybridisation (CGH) and fluorescence in situ hybridisation (FISH) using partial chromosome paints and a locus-specific YAC clone revealed a de novo direct duplication of the chromosomal region 16q11.2-q13 leading to a partial trisomy 16q (46,XX,dup(16)(q11.2q13)). There are only five postnatal reports of comparable duplications involving this chromosomal region. These patients presented with little or no associated dysmorphic features but with significant neurodevelopmental delay and severe behavioural problems. After genetic counselling, the parents opted for termination of pregnancy. Post-mortem examination showed slight facial dysmorphic signs, minor dysgenesis of the ovaries and an atypical outflow of the arteria thyroidea ima.

Molecular characterization of partial trisomy 16q24.1-qter: clinical report and review of the literature

We describe a 3(1/2)-year-old girl with psychomotor and mental retardation; dysmorphic features, including a high forehead with bitemporal narrowing; a broad nasal bridge and a broadened nose; downslanting palpebral fissures; abnormal ears; vertebral abnormalities; cardiac defect; genital hypoplasia; and anal abnormalities. The karyotype of our patient (550 bands) was normal. Molecular cytogenetic techniques, including comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH), revealed that this girl was a carrier of a de novo derivative chromosome 7 arising from a cryptic t(7;16)(p22.3;q24.1) translocation generating a trisomy 16q24.1-qter and a 7p22.3-pter deletion. FISH with a series of specific chromosome 7p and 16q probes allowed us to delineate the chromosome 7 breakpoint between YAC660G6 (WD7S517) and YAC848A12 (D7S521, D7S31, and WI-4829) and the chromosome 16 breakpoint between BAC457K7 (D42053) and BAC44201 (SGC30711). The comparison of the clinical features of our patient with those of 2 cases of pure terminal 7p deletion and 28 cases of trisomy 16q reported in the literature allowed us to establish the following phenotype-genotype correlation for trisomy of the long arm of chromosome 16: distinctive facies (high/prominent forehead, bitemporal narrowing, periorbital edema in the neonatal period); severe mental retardation; vertebral, genital, and anal abnormalities to 16q24; distal joint contractures and camptodactyly to 16q23; cleft palate and renal anomalies to 16q22; beaked nose and gall bladder agenesis to 16q21; gut malrotation; lung and liver anomalies to 16q13; and behavior abnormalities to band 16q11-q13.

Anisomastia associated with interstitial duplication of chromosome 16, mental retardation, obesity, dysmorphic facies, and digital anomalies: molecular mapping of a new syndrome by fluorescent in situ hybridization and microsatellites to 16q13 (D16S419-D16S503)

Anisomastia is a common problem among developing adolescent girls. We recently evaluated a 22-yr-old female patient who had severe anisomastia (which had been repaired by surgery), associated with moderate to severe mental retardation, a stocky body habitus with mild obesity, dysmorphic facies (prominent, upslanting palpebral fissures, beaked nose, and a prominent philtrum), webbed neck, low hairline, and severe bilateral clinodactyly of the third, fourth, and fifth fingers with acral (but not large joint) flexion contractures. A peripheral blood high resolution karyotype revealed additional chromosomal material within the long arm of chromosome 16. Densitometric analysis of amplified polymorphic sequence-tagged sites (STS) mapping to 16q suggested that the duplication is defined by the noninvolved markers D16S419 [16q12-cen, 66 centimorgan (cM) from 16p terminus] and D16S421 (16q13-q21, 84.4 cM), encompassing a maximum of 18.4 cM of genetic distance. The STS analysis showed that the duplication was on the maternally derived chromosome 16, resulting in two maternal (and one paternal) copies of that region of chromosome 16. The location was further confirmed by bacterial artificial chromosomes (BACs) that were obtained from a commercially available library, labeled, and used for fluorescence in situ hybridization. The BACs containing STSs D16S408, D16S3137, and D16S3032 (markers that correspond to 16q13) showed two regions of hybridization, indicating that these sites were duplicated, whereas a BAC containing the STS D16S512 (which corresponds to 16q21-q22) revealed one hybridization signal per 16q, indicating that the corresponding region was not involved in the duplication. The distance between the probe signals suggested a tandem duplication. We conclude that even though trisomy 16 is the most common autosomal trisomy in spontaneous abortions, few patients with unbalanced chromosome 16 abnormalities survive to adulthood; in this report we describe one such patient with an interstitial chromosome 16 duplication (at 16q13), who had a specific phenotype associated with abnormal breast size. There are clinical similarities between this patient and patients with other 16q abnormalities, although the breast findings were unique. Molecular cytogenetics, including fluorescence in situ hybridization and densitometric analysis of amplified STSs, provided useful tools for the precise mapping of the syndrome to 16q13, where the gene(s) responsible for this phenotype might be localized.