Effects of IKAP/hELP1 Deficiency on Gene Expression in Differentiating Neuroblastoma Cells: Implications for Familial Dysautonomia

Abstract

Familial dysautonomia (FD) is a developmental neuropathy of the sensory and autonomous nervous systems. The IKBKAP gene, encoding the IKAP/hELP1 subunit of the RNA polymerase II Elongator complex is mutated in FD patients, leading to a tissue-specific mis-splicing of the gene and to the absence of the protein in neuronal tissues. To elucidate the function of IKAP/hELP1 in the development of neuronal cells, we have downregulated IKBKAP expression in SHSY5Y cells, a neuroblastoma cell line of a neural crest origin. We have previously shown that these cells exhibit abnormal cell adhesion when allowed to differentiate under defined culture conditions on laminin substratum. Here, we report results of a microarray expression analysis of IKAP/hELP1 downregulated cells that were grown on laminin under differentiation or non-differentiation growth conditions. It is shown that under non-differentiation growth conditions, IKAP/hELP1 downregulation affects genes important for early developmental stages of the nervous system, including cell signaling, cell adhesion and neural crest migration. IKAP/hELP1 downregulation during differentiation affects the expression of genes that play a role in late neuronal development, in axonal projection and synapse formation and function. We also show that IKAP/hELP1 deficiency affects the expression of genes involved in calcium metabolism before and after differentiation of the neuroblastoma cells. Hence, our data support IKAP/hELP1 importance in the development and function of neuronal cells and contribute to the understanding of the FD phenotype.

Axon Transport and Neuropathy

“…101e106 Elp1 is a constituent of the heterohexameric transcriptional elongator complex 107 ; therefore, it may be involved in transcriptional regulation. 102,103,108 Interestingly, however, a significant amount of Elp1 protein is found in a vesicular pattern in the cytoplasm of both nonneuronal cells 104,109 and neurons ( Figure 1B), suggesting that it has a function apart from transcription. Elp1 function in the neuron cytoplasm (axons and dendrites) could be important for signaling processes required for their normal development and innervation homeostasis, but whether this has any relevance to neuron survival and differentiation in FD is not clear.…”

Genome-wide analysis of familial dysautonomia and kinetin target genes with patient olfactory ecto-mesenchymal stem cells

“…Four previous studies from other laboratories have generated a wealth of data on the transcriptome variations in either FD or IKBKAP knockdown samples [Cheishvili et al, 2007; Close et al, 2006; Cohen‐Kupiec et al, 2011; Lee et al, 2009]. Therefore, we procured the raw data from all studies and reanalyzed the data in search for the common candidates that may be involved in FD physiopathology.…”

“…Lee and colleagues determined that the neuron‐specific splicing factor NOVA1 was underexpressed in FD versus control‐induced pluripotent stem cell (iPSC) derived neural crest precursors [Lee et al, 2009]. Finally, a recent study showed that FD affects genes important for early developmental stages of the nervous system using neuroblastoma cell lines [Cohen‐Kupiec et al, 2011]. Nevertheless, the specific means by which aberrant IKBKAP mRNA splicing causes the disease producing developmental and degenerative neuronal changes in FD neurons is still unclear.…”

A neuron autonomous role for the familial dysautonomia geneELP1in sympathetic and sensory target tissue innervation

“…Several studies have examined transcriptional deregulation in cells isolated from individuals with FD or in heterologous cells after reduction of Elp1 by shRNA-mediated interference, but how the myriad of genes identified as potential Elp1 targets have a role in sympathetic and sensory neuron target tissue innervation in FD remains unclear (Cheishvili et al, 2007;Close et al, 2006;Cohen-Kupiec et al, 2011;Lee et al, 2009). Several studies have implicated Elp1 in cell migration, such as through its interaction with filamin A to regulate actin cytoskeleton reorganization during migration or by regulating α-tubulin acetylation in stabilized MTs, which are essential for neuron migration, neurite outgrowth and intracellular trafficking (Creppe et al, 2009;Solinger et al, 2010).…”