Alternative Splicing of the Histone Demethylase LSD1/KDM1 Contributes to the Modulation of Neurite Morphogenesis in the Mammalian Nervous System

Abstract

A variety of chromatin remodeling complexes are thought to orchestrate transcriptional programs that lead neuronal precursors from earliest commitment to terminal differentiation. Here we show that mammalian neurons have a specialized chromatin remodeling enzyme arising from a neurospecific splice variant of LSD1/KDM1, histone lysine specific demethylase 1, whose demethylase activity on Lys4 of histone H3 has been related to gene repression. We found that alternative splicing of LSD1 transcript generates four full-length isoforms from combinatorial retention of two identified exons: the 4 aa exon E8a is internal to the amine oxidase domain, and its inclusion is restricted to the nervous system. Remarkably, the expression of LSD1 splice variants is dynamically regulated throughout cortical development, particularly during perinatal stages, with a progressive increase of LSD1 neurospecific isoforms over the ubiquitous ones. Notably, the same LSD1 splice dynamics can be fairly recapitulated in cultured cortical neurons. Functionally, LSD1 isoforms display in vitro a comparable demethylase activity, yet the inclusion of the sole exon E8a reduces LSD1 repressor activity on a reporter gene. Additional distinction among isoforms is supported by the knockdown of neurospecific variants in cortical neurons resulting in the inhibition of neurite maturation, whereas overexpression of the same variants enhances it. Instead, perturbation of LSD1 isoforms that are devoid of the neurospecific exon elicits no morphogenic effect. Collectively, results demonstrate that the arousal of neuronal LSD1 isoforms pacemakes early neurite morphogenesis, conferring a neurospecific function to LSD1 epigenetic activity.

Overexpression of the shortest isoform of histone demethylase LSD1 primes hematopoietic stem cells for malignant transformation

“…Although the neuron-specific expression of exon 8a-retaining splice variants has been reported previously, 15 no information is available regarding the expression pattern and biological functions of LSD1 isoforms in the hematopoietic system. To address this issue, we attempted to detect LSD1 isoforms discriminately using isoform-specific RT-PCR (supplemental Table 1).…”

“…15,24 TCRb rearrangement was analyzed by genomic PCR according to Shen et al 25 Primer sequences are listed in supplemental …”

“…2 from variants 1 and 2 as described by Zibetti et al 15 Lentiviral expression vectors were constructed by inserting full-length cDNAs into a CSII-CMV-MCS-IRES DsRed vector as reported. 26 …”

“…14 Moreover, LSD1 has 4 isoforms with different histone demethylating activities and affinities to CoREST, offering an additional layer of functional regulation. 15 hairpin RNA (shRNA)-mediated knockdown of LSD1 impairs maturation of blood cells in association with the expansion of undifferentiated hematopoietic stem/progenitor cells (HSPCs) and committed progenitors in mice. On the other hand, LSD1 was shown to be essential for the self-renewal and proper differentiation of HSCs in conditional LSD1 knockout mice.…”

Targeted Epigenetic Modulation of Gene Expression in the Brain

“…Epigenetic processes are implicated in psychiatric disorders, including depression and drug addiction (Jakovcevski and Akbarian, 2012;Nestler et al, 2015;Walker et al, 2015). Additionally, the basic mechanisms underlying epigenetic processes may show subtle but important differences due to brain-specific splice variation and differential isoform expression (e.g., Zibetti et al, 2010). Determining the causal role of epigenetic modifications and the resulting effects on neural systems and behavior requires the use of technologies capable of experimentally inducing specific epigenetic marks at discrete genetic loci.…”