Transcription profiling by array of hematopoietic stem and progenitor cells from APCmin mice

Apc, a negative regulator of the canonical Wnt signaling pathway, is a bona-fide tumor suppressor whose loss of function results in intestinal polyposis. APC is located in a commonly deleted region on human chromosome 5q, associated with myelodysplastic syndrome (MDS) suggesting that haploinsufficiency of APC contributes to the MDS phenotype. Analysis of the hematopoietic system of mice with the Apcmin allele that results in a premature stop codon and loss of function, showed no abnormality in steady state hematopoiesis. Bone marrow derived from Apcmin mice showed enhanced repopulation potential, indicating of a cell intrinsic gain of function in the long-term hematopoietic stem cell (HSC) population. However, Apcmin bone marrow was unable to repopulate secondary recipients due to loss of the quiescent HSC population. Apcmin mice developed a myelodysplastic/ myeloproliferative phenotype. Our data indicate that Wnt activation through haploinsufficiency of Apc causes insidious loss of HSC function that is only evident in serial transplantation strategies. These data provide a cautionary note for HSC expansion strategies through Wnt pathway activation, provide evidence that cell extrinsic factors can contribute to the development of myeloid disease and indicate that loss of function of APC may contribute to the phenotype observed in patients with MDS and del(5q). LKS+ cells were isolated from Apcmin or WT mice using high-speed multiparameter flow cytometry. At least 2x104 cells per mouse were isolated with confirmed purity in excess of 90%. The cells were treated with RLT lysis buffer (Qiagen) containing beta-mercaptoethanol to stabilize RNA. RNA was extracted using Qiagen RNeasy Micro Kit according to manufacturers instruction. The RNA was amplified using a linear amplification protocol (Nugen Ovation V2 amplification system). cDNA was fragmented and biotinylated before hybridization onto Affymetrix mouse genome 430 2.0 Array chips