Circadian Rhythm-Dependent Alterations of Gene Expression in Drosophila Brain Lacking Fragile X Mental Retardation Protein

Fragile X syndrome is caused by the loss of the FMR1 gene product, fragile X mental retardation protein (FMRP). The loss of FMRP leads to altered circadian rhythm behaviors in both mouse and Drosophila; however, the molecular mechanism behind this phenomenon remains elusive. Here we performed a series of gene expression analyses, including of both mRNAs and microRNAs (miRNAs), and identified a number of mRNAs and miRNAs (miRNA-1 and miRNA-281) with circadian rhythm-dependent altered expression in dfmr1 mutant flies. Identification of these RNAs lays the foundation for future investigations of the molecular pathway(s) underlying the altered circadian rhythms associated with loss of dFmr1

Gene expression profiling in wild-type and dfmr1 null mutant fly heads.

<p><b>A.</b> Quantitative RT-PCR was used to measure the levels of the indicated transcripts in both <i>w¹¹¹⁸</i> and <i>dfmr1</i> null fly heads between CT00 and CT24. <b>B.</b> Frequency distribution of gene expression levels in different genotypes. <b>C.</b> Venn diagram showing the number of genes with significant and consistent changes (≥1.5 fold) in <i>dfmr1</i> null mutant fly heads at CT00 and CT12, and the overlap between two time points.</p

The loss of dFmr1 leads to altered expression and biogenesis of miR-1 and miR-281.

<p>Quantitative RT-PCR was used to measure the levels of pri-, pre-, and mature forms of miR-1 (A) and miR-281 (B) in <i>w¹¹¹⁸</i> and <i>dfmr1</i> null fly heads. The relative expression levels as determined by ΔΔCt analyses are shown. Values are mean ± SD for triplicate samples. *: P<0.001.</p

Validation of altered gene expression by real-time PCR.

<p>Quantitative RT-PCR was used to measure the levels of the indicated transcripts in both <i>w¹¹¹⁸</i> and <i>dfmr1</i> null fly heads.</p