Zebrafish, Chicken Genome Gives Clues to Deleted Regions in Human CLL

[Guest guest]

[295] The 13q and 11q B-Cell Chronic Lymphocytic Leukemia Deleted

Regions Derive from a Common Ancestral Region in the Zebrafish on

Linkage Group 9. Session Type: Oral Session

L. Auer, Sophia Riaz, Finbarr E. Cotter (Intr. by

Newland) Centre for Haematology, Barts The London Queen School

of Medicine, London, United Kingdom

Loss of the long arm of chromosomes 11 and 13 are the most consistent

cytogenetic abnormalities for patients with B-cell chronic

lymphocytic leukemia (B-CLL). They suggest the presence of as yet

unidentified tumor suppressor genes within well defined minimal

deleted regions (MDRs).

The use of small vertebrate organisms, such as the zebrafish, as

models of diseases associated with chromosomal deletions enables the

functional analysis of potential causative genes. Hemopoiesis is well

conserved between the zebrafish and human and conserved synteny

exists between the two genomes.

In this study, the evolutionary conservation between the zebrafish

and human genome is investigated for the 13q14 and 11q22-23 regions

deleted in B-CLL. Zebrafish orthologs have been identified and

radiation hybrid (RH) mapping performed to confirm their chromosomal

location and define regions of conserved synteny.We have identified

38 zebrafish orthologs of the human genes in the MDRs in zebrafish

cDNA and the syntenic regions for the human deletions in the

zebrafish genome. The 13q14 region was syntenic with two main regions

in the zebrafish genome, namely linkage group 1 (LG1) and LG9.

The majority of zebrafish orthologs to 11q22-23 were found on LG5,

LG15 and LG21. One syntenic region, LG9, in the zebrafish genome is

of potential interest. Analysis of the smallest critical region of

deletion in B-CLL for both 11q22-23 and 13q14 reveals that the human

gene equivalents are contained within an area of 22.02 cR on LG9

(approximately 3260 kb). Within LG9, orthologs to two genes to human

chromosome 11, three to human chromosome 13 and two chromosome 13

microRNAs (mir-15a and mir-16-1) were identified.

The critical region on zebrafish LG9 maps to the MDR for both human

chromosomes, suggesting a common ancestry for the B-CLL tumor

suppressor genes. This is further supported by analysis of the

chicken genome where the same 5 genes from 13q14 and 11q22-23

(C13orf1, RFP2, FLJ11712, FDX1, ARHGAP20) lie within a 10.04 Mb

region on chromosome 1. In addition, TILLING for knock-outs of genes

in this region of zebrafish embryos will allow analysis of their in

vivo potential for lymphoproliferation and may define prime causative

genes for B-CLL within human chromosomes 11q and 13q by reverse

genetics.

Our study provides an explanation for involvement of both 11q and 13q

in B-CLL and the potential to develop animal models for this common

lymphoproliferative disorder.