Interstitial 16p13.3 microduplication: case report and critical review of genotype-phenotype correlation

Subphenotype meta-analysis of testicular cancer genome-wide association study data suggests a role for RBFOX family genes in cryptorchidism susceptibility

STUDY QUESTION

Can subphenotype analysis of genome-wide association study (GWAS) data from subjects with testicular germ cell tumor (TGCT) provide insight into cryptorchidism (undescended testis, UDT) susceptibility?

SUMMARY ANSWER

Suggestive intragenic GWAS signals common to UDT, TGCT case-case and TGCT case-control analyses occur in genes encoding RBFOX RNA-binding proteins (RBPs) and their neurodevelopmental targets.

WHAT IS KNOWN ALREADY

UDT is a strong risk factor for TGCT, but while genetic risk factors for TGCT are well-known, genetic susceptibility to UDT is poorly understood and appears to be more complex.

STUDY DESIGN, SIZE, DURATION

We performed a secondary subphenotype analysis of existing GWAS data from the Testicular Cancer Consortium (TECAC) and compared these results with our previously published UDT GWAS data, and with data previously acquired from studies of the fetal rat gubernaculum.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Studies from the National Cancer Institute (NCI), United Kingdom (UK) and University of Pennsylvania (Penn) that enrolled white subjects were the source of the TGCT GWAS data. We completed UDT subphenotype case-case (TGCT/UDT vs TGCT/non-UDT) and case-control (TGCT/UDT vs control), collectively referred to as 'TECAC' analyses, followed by a meta-analysis comprising 129 TGCT/UDT cases, 1771 TGCT/non-UDT cases, and 3967 unaffected controls. We reanalyzed our UDT GWAS results comprising 844 cases and 2718 controls by mapping suggestive UDT and TECAC signals (defined as P < 0.001) to genes using Ingenuity Pathway Analysis (IPA®). We compared associated pathways and enriched gene categories common to all analyses after Benjamini-Hochberg multiple testing correction, and analyzed transcript levels and protein expression using qRT-PCR and rat fetal gubernaculum confocal imaging, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

We found suggestive signals within 19 genes common to all three analyses, including RBFOX1 and RBFOX3, neurodevelopmental paralogs that encode RBPs targeting (U)GCATG-containing transcripts. Ten of the 19 genes participate in neurodevelopment and/or contribute to risk of neurodevelopmental disorders. Experimentally predicted RBFOX gene targets were strongly overrepresented among suggestive intragenic signals for the UDT (117 of 628 (19%), P = 3.5 × 10-24), TECAC case-case (129 of 711 (18%), P = 2.5 × 10-27) and TECAC case-control (117 of 679 (17%), P = 2 × 10-21) analyses, and a majority of the genes common to all three analyses (12 of 19 (63%), P = 3 × 10-9) are predicted RBFOX targets. Rbfox1, Rbfox2 and their encoded proteins are expressed in the rat fetal gubernaculum. Predicted RBFOX targets are also enriched among transcripts differentially regulated in the fetal gubernaculum during normal development (P = 3 × 10-31), in response to in vitro hormonal stimulation (P = 5 × 10-45) and in the cryptorchid LE/orl rat (P = 2 × 10-42).

LARGE SCALE DATA

GWAS data included in this study are available in the database of Genotypes and Phenotypes (dbGaP accession numbers phs000986.v1.p1 and phs001349.v1p1).

LIMITATIONS, REASONS FOR CAUTION

These GWAS data did not reach genome-wide significance for any individual analysis. UDT appears to have a complex etiology that also includes environmental factors, and such complexity may require much larger sample sizes than are currently available. The current methodology may also introduce bias that favors false discovery of larger genes.

WIDER IMPLICATIONS OF THE FINDINGS

Common suggestive intragenic GWAS signals suggest that RBFOX paralogs and other neurodevelopmental genes are potential UDT risk candidates, and potential TGCT susceptibility modifiers. Enrichment of predicted RBFOX targets among differentially expressed transcripts in the fetal gubernaculum additionally suggests a role for this RBP family in regulation of testicular descent. As RBFOX proteins regulate alternative splicing of Calca to generate calcitonin gene-related peptide, a protein linked to development and function of the gubernaculum, additional studies that address the role of these proteins in UDT are warranted.

STUDY FUNDING/COMPETING INTEREST(S)

The Eunice Kennedy Shriver National Institute for Child Health and Human Development (R01HD060769); National Center for Research Resources (P20RR20173), National Institute of General Medical Sciences (P20GM103464), Nemours Biomedical Research, the Testicular Cancer Consortium (U01CA164947), the Intramural Research Program of the NCI, a support services contract HHSN26120130003C with IMS, Inc., the Abramson Cancer Center at Penn, National Cancer Institute (CA114478), the Institute of Cancer Research, UK and the Wellcome Trust Case-Control Consortium (WTCCC) 2. None of the authors reports a conflict of interest.

A novel unbalanced translocation between the short arms of chromosomes 6 and 16 in a newborn girl: Clinical features and management

The reporting of previously undescribed genetic mutations and resulting clinical phenotypes guides management and enables a more accurate prognosis for clinicians treating newborns with similar features. Previous cases of 6p deletions and 16p duplications have been described as separate entities. This patient presents with both and has a unique phenotype.

16p13 microduplication without CREBBP involvement: Moving toward a phenotype delineation

The short arm of chromosome 16 is one of the less stable regions of our genome, as over 10% of the euchromatic region of 16p is composed of highly complex low copy repeats that are known to be predisposed to rearrangements mediated by non-allelic homologous recombination. The 16p13.3p13.13 molecular region has been defined as the 16p duplication hotspot, and duplications of chromosome 16p13 have recently been confirmed to cause a recognizable syndrome, with CREBBP being the main phenotype-causing gene. To date, only one case report is present in the literature with a 16p13 duplication without CREBBP involvement; we describe here a second analogous case with a not previously reported 16p13.2p13.13 microduplication. This paper allows us to better delineate the clinical features of 16p13 microduplications that do not encompass CREBBP and, concurrently, to narrow the molecular region responsible for congenital heart defects in 16p duplications as well as to propose GRIN2A as a candidate gene for epilepsy.

Maternally inherited autosomal dominant intellectual disability caused by 16p13.3 microduplication

A 16p13.3 duplication syndrome has been recently suggested to be a novel recognizable syndrome as a reciprocal microduplication disease of Rubinstein-Taybi syndrome. The CREBBP gene is believed to be the dosage-sensitive critical gene responsible for the reciprocal duplication and deletion syndrome. Descriptions so far have been de novo. Here, we report a very rare case of a maternally inherited a -1 Mb sized duplication on 16p13.3 identified by SNP array testing. The patient showed moderate intellectual disability, normal growth, and characteristic facial features. The patient's mother also had mild intellectual disability, normal growth, camptodactyly, proximally implanted small thumbs, and distinctive facial features. The study provides additional information that furthers the understanding and delineation of 16p13.3 duplication syndrome.

Genotype-phenotype correlation of 16p13.3 terminal duplication and 22q13.33 deletion: Natural history of a patient and review of the literature

This article reports a patient with a de novo ∼ 9.32 Mb duplication at 16p13.3 and a ∼ 71 Kb deletion at 22q13.33. The patient was followed from 1 month old to 3 years and 8 months of age and presented typical features of the 16p13.3 duplication syndrome. In addition, the patient presents a portal cavernoma, an alteration rarely reported in this condition. Renal agenesis was detected as additional developmental defect. After genomic array and FISH analysis, the karyotype was 46,XX,ins(22;16)(q13;p13.2p13.3). ish ins(22;16)(RP11-35P16+, RP11-27M24+). arr16p13.2p13.3(85,880-9,413,353)×3 dn arr22q13.33 (51,140,789-51,197,838)×1 dn. The authors provide a comprehensive review of the literature. This approach shed light on the genotype-phenotype correlation.

All-or-(N)One - an epistemological characterization of the human tumorigenic neuronal paralogous FAM72 gene loci

FAM72 is a novel neuronal progenitor cell (NPC) self-renewal supporting protein expressed under physiological conditions at low levels in other tissues. Accumulating data indicate the potential pivotal tumourigenic effects of FAM72. Our in silico human genome-wide analysis (GWA) revealed that the FAM72 gene family consists of four human-specific paralogous members, all of which are located on chromosome (chr) 1. Unique asymmetric FAM72 segmental gene duplications are most likely to have occurred in conjunction with the paired genomic neighbour SRGAP2 (SLIT-ROBO Rho GTPase activating protein), as both genes have four paralogues in humans but only one vertebra-emerging orthologue in all other species. No species with two or three FAM72/SRGAP2 gene pairs could be identified, and the four exclusively human-defining ohnologues, with different mutation patterns in Homo neanderthalensis and Denisova hominin, may remain under epigenetic control through long non-coding (lnc) RNAs.

16p13.3 duplication associated with non-syndromic pierre robin sequence with incomplete penetrance

BACKGROUND

Pierre Robin sequence (PRS) is a condition present at birth. It is characterized by micrognathia, cleft palate, upper airway obstruction, and feeding problems. Multiple etiologies including genetic defects have been documented in patients with syndromic, non-syndromic, and isolated PRS.

CASE PRESENTATION

We report a 4-year-old boy with a complex small supernumerary marker chromosome (sSMC) who had non-syndromic Pierre Robin sequence (PRS). The complex marker chromosome, der(14)t(14;16)(q11.2;p13.13), was initially identified by routine chromosomal analysis and subsequently characterized by array-comparative genomic hybridization (array CGH) and confirmed by fluorescence in situ hybridization (FISH). Clinical manifestations included micrognathia, U-type cleft palate, bilateral congenital ptosis, upslanted and small eyes, bilateral inguinal hernias, umbilical hernia, bilateral clubfoot, and short fingers and toes. To our best knowledge, this was the first case diagnosed with non-syndromic PRS associated with a complex sSMC, which involved a 3.8 Mb gain in the 14q11.2 region and an 11.8 Mb gain in the 16p13.13-pter region.

CONCLUSIONS

We suggest that the duplicated chromosome segment 16p13.3 possibly may be responsible for the phenotypes of our case and also may be a candidate locus of non-syndromic PRS. The duplicated CREBBP gene within chromosome 16p13.3 is associated with incomplete penetrance regarding the mandible development anomalies. Further studies of similar cases are needed to support our findings.

Phenotypic expansion of the interstitial 16p13.3 duplication: a case report and review of the literature

Genotype-phenotype analysis of at least 25 individuals with interstitial 16p13.3 duplications defines a recognizable syndrome associated with duplication of a critical Rubinstein-Taybi region encompassing only the CREBBP gene. Nevertheless, variable or incompletely penetrant phenotype has been reported previously. We here report a case of a 5-year old boy with a recognizable phenotype of this syndrome, including intellectual disability, mild arthrogryposis, small and proximally implanted thumbs and characteristic facial features. In addition, growth delay, microcephaly and distinguishable structural brain MRI abnormalities were observed. A de novo 1.5 Mb interstitial duplication of 16p13.3 was detected by SNP-array and fluorescence in situ hybridization (FISH). Short tandem repeat polymorphism (STRP) analysis with marker D16S475 indicated that the duplication was formed before maternal meiosis II. Our findings highlight the variable clinical features and further expand the phenotypic spectrum correlated with this lately proposed syndrome.

A de novo 11p13 Microduplication in a Patient with Some Features Invoking Silver-Russell Syndrome

Patients with Silver-Russell syndrome (SRS) show an intrauterine and postnatal growth restriction associated with a variable spectrum of additional features. Genetic or epigenetic alterations on chromosomes 7 and 11 can be detected in several SRS patients; however, a large fraction of cases remains with unknown genetic etiology. Here, we describe the clinical and molecular findings of a patient with a phenotype invoking SRS showing intrauterine and postnatal growth retardation, psychomotor retardation, relative macrocephaly, slightly triangular face with pointed chin, clinodactyly, and a slight body asymmetry, in whom single-nucleotide polymorphism oligonucleotide array analysis led to the identification of a de novo 11p13 duplication containing many genes that could be functionally related with the observed clinical features. Many deletions of chromosome 11p13, resulting in WAGR (Wilms tumor, aniridia, genital anomalies, mental retardation) syndrome, have been described, while only few duplications spanning the same region have been reported so far. To our knowledge, this is the first reported case presenting a SRS carrier of an 11p13 duplication. We propose candidate genes for the observed traits, and in particular, we discuss the possible role of the involvement of 2 noncoding RNAs in the etiology of the phenotype.