Specific amplifications and copy number decreases during human neural stem cells differentiation towards astrocytes, neurons and oligodendrocytes.

Ulrike Fischer,Ella Kim,Eckart Meese,Andreas Keller

doi:10.18632/oncotarget.15980

Abstract

There is growing evidence that gene amplifications are an attribute of normal cells during development and differentiation. During neural progenitor cell differentiation half of the genome is involved in amplification process. To answer the question how specific amplifications occur at different stages and in different lineages of differentiation we analyzed the genes CDK4, MDM2, EGFR, GINS2, GFAP, TP53, DDB1 and MDM4 in human neural stem cells that were induced to differentiate towards astrocytes, neurons and oligodendrocytes. We found specific amplification pattern for each of the eight analyzed genes both in undifferentiated neural stem and progenitor cells and in cells that were induced for differentiation. Different amplification patterns were also found between adherently grown neural stem cells and cells that were grown as spheres. The most frequently amplified genes were MDM2 and CDK4 with the latter amplified in all three lineages at all analyzed stages. Amplification of the analyzed genes was also found in four glioma stem-like cells. The combined amplification data of stem cells and of tumor stem cells can help to define cell populations at the origin of the tumor. Furthermore, we detected a decrease of gene copies at specific differentiation stages most frequently for MDM4. This study shows specific amplification pattern in defined stem cell populations within specific time windows during differentiation processes indicating that amplifications occur in an orderly sequence during the differentiation of human neural stem and progenitor cells.

Highlights

There is ample evidence for gene amplifications in human tumors [1, 2]
To answer the question how specific amplifications occur at different stages and in different lineages of differentiation we analyzed the genes CDK4, MDM2, EGFR, GINS2, GFAP, TP53, DDB1 and MDM4 in human neural stem cells that were induced to differentiate towards astrocytes, neurons and oligodendrocytes
For all lineages of differentiation and all time points we determined the copy number of eight genes including CDK4, MDM2, EGFR, GINS2, GFAP, TP53, DDB1 and MDM4 all of which are known to localize to amplified genomic regions in neural progenitor cells during differentiation and to be amplified in human glioblastoma

Summary

Introduction

Several studies reported gene amplification in stem cells or progenitor cells during developmental processes and during differentiation. We detected gene amplifications during the differentiation of human and mouse myoblasts towards muscle cells [7]. Our abovementioned studies on the differentiation of human and mouse myoblasts towards muscle cells provided first evidence for ordered amplification events. We set out to answer the question whether amplifications occur in an orderly sequence as part of the differentiation of human neural stem cells. To this end, we compared the sequence of amplification events during three different lineages of differentiation and ask for the specificity of an amplification pattern for each of these processes. We differentiated neural stem cells towards astrocytes, neurons and oligodendrocytes to investigate gene amplifications

Methods

Results

Conclusion