PLoS One. 2010 Aug 25;5(8):e12375. doi: 10.1371/journal.pone.0012375.

Bilateral renal agenesis/hypoplasia/dysplasia (BRAHD): postmortem analysis of 45 cases with breakpoint mapping of two de novo translocations.

Harewood L, Liu M, Keeling J, Howatson A, Whiteford M, Branney P, Evans M, Fantes J, Fitzpatrick DR.

Source

MRC Human Genetics Unit, Institute of Genetic and Molecular Medicine, Edinburgh, United Kingdom.

Abstract

BACKGROUND:

Bilateral renal agenesis/hypoplasia/dysplasia (BRAHD) is a relatively common, lethal malformation in humans. Established clinical risk factors include maternal insulin dependent diabetes mellitus and male sex of the fetus. In the majority of cases, no specific etiology can be established, although teratogenic, syndromal and single gene causes can be assigned to some cases.

METHODOLOGY/PRINCIPAL FINDINGS:

45 unrelated fetuses, stillbirths or infants with lethal BRAHD were ascertained through a single regional paediatric pathology service (male:female 34:11 or 3.1:1). The previously reported phenotypic overlaps with VACTERL, caudal dysgenesis, hemifacial microsomia and Müllerian defects were confirmed. A new finding is that 16/45 (35.6%; m:f 13:3 or 4.3:1) BRAHD cases had one or more extrarenal malformations indicative of a disoder of laterality determination including; incomplete lobulation of right lung (seven cases), malrotation of the gut (seven cases) and persistence of the left superior vena cava (five cases). One such case with multiple laterality defects and sirelomelia was found to have a de novo apparently balanced reciprocal translocation 46,XY,t(2;6)(p22.3;q12). Translocation breakpoint mapping was performed by interphase fluorescent in-situ hybridization (FISH) using nuclei extracted from archival tissue sections in both this case and an isolated bilateral renal agenesis case associated with a de novo 46,XY,t(1;2)(q41;p25.3). Both t(2;6) breakpoints mapped to gene-free regions with no strong evidence of cis-regulatory potential. Ten genes localized within 500 kb of the t(1;2) breakpoints. Wholemount in-situ expression analyses of the mouse orthologs of these genes in embryonic mouse kidneys showed strong expression of Esrrg, encoding a nuclear steroid hormone receptor. Immunohistochemical analysis showed that Esrrg was restricted to proximal ductal tissue within the embryonic kidney.

CONCLUSIONS/SIGNIFICANCE:

The previously unreported association of BRAHD with laterality defects suggests that renal agenesis may share a common etiology with heterotaxy in some cases. Translocation breakpoint mapping identified ESRRG as a plausible candidate gene for BRAHD.

PMID:: 20811621; [PubMed - indexed for MEDLINE]
PMCID:: PMC2928268

Free PMC Article

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Figure 2

Mapping of the t(1;2) breakpoints using interphase FISH analysis.

As no metaphase spreads or viable cells were available from this case, interphase mapping was performed using dissociated nuclei from archival tissue sections. The mapping of each clone was confirmed on multiple nuclei to confirm the presence or absence of co-localization. A. Two representative nuclei used to map probes flanking the 1q breakpoint. On the left is the merged color image with the green and red channels of the same image shown in the middle and the right-hand-side respectively. The top nucleus shows co-localization of the FISH signals for RP11-22M7 and RP4-723P6 on both chromosomes (white arrows), which together with other results shown in Table S2, can be used to map the more telomeric probe (RP4-723P6) to the der(1). The lower nucleus demonstrates the utility of chromosome arm paints in interphase mapping. The green channel image shows three clear 1q chromosomal paint domains within the nucleus. On the basis of the relative volume of these domains and with knowledge of the cytogenetic location of the translocation breakpoint, it is possible to assign these domains to the normal chromosome 1 (1(N), the largest domain) and the derivative chromosomes (der(1), middle-sized domain and der(2), smallest domain). It can be seen that the RP11-239I22 probe maps to the der(2) and is therefore distal to the 1q breakpoint. B. The physical map of the breakpoint region of 1q with the orange box indicating the region of genomic DNA that could plausibly contain the breakpoint. There are only two genes in this region with one of these, USH2A, being directly disrupted by the breakpoint. C. Two representative nuclei used in mapping the 2p breakpoint. The overall configuration is identical to A. The upper nucleus shows colocalization of RP11-410L9 with a probe (RP11-352J11) that has been shown to map telomeric of the 2p breakpoint. The lower nucleus shows failure of colocalization of RP11-568H24 on one allele, showing that this maps to the der(2). D. The physical map of the breakpoint region (orange box) on 2p. Unfortunately, it was not possible to map this breakpoint further. Five genes could plausibly be disrupted by this breakpoint; TSSC1, TTC15, ADI1, RNASEH1 and RPS7.

Bilateral Renal Agenesis/Hypoplasia/Dysplasia (BRAHD): Postmortem Analysis of 45 Cases with Breakpoint Mapping of Two De Novo Translocations

PLoS One. 2010;5(8):e12375.