Age-Dependent Gene Expression of Blow Fly Lucilia cuprina (Diptera: Calliphoridae) during Egg Development Improving Age Estimation in Forensic Entomology

Abstract

Estimating the age of immature stages of necrophagous flies developing on corps, may provide clues for understanding the minimum post-mortem intervals (PMI) to aid death investigation. It can be hard to comprehend precisely the interval age of developmental stage that does not increase in size including egg. In this study we investigated the feasibility of predicting egg age from ovi-position to hatching over 2 hour’s intervals of egg development. The expression profile of three genes, cuticle I, Ecdysone receptor (EcR) and chymotrypsin of lucilia cuprina (Diptera: Calliphoridae) were determined at 2, 6, and 8 hours of egg development. Semi-quantitative reverse transcriptase (RT)-PCR were applied for profiling of indicated genes expressions from eggs of different developmental stages by designing specific primers sets. Target transcripts were then quantified from the gel using image J and syn gene programs. The results indicated time-dependent expressions of the three genes with significant increase at the selected time points. Cuticle 1 expression was increased up to 2, 25 and 6 folds at 4, 6 and 8 hours respectively when compared to 2 hours expression level. Likewise a significant induction of both chymotrypsin and EcR (around 1.2, 1.7 then 1.2 and 3, 2, 6 folds, respectively) during 4, 6 and 8 hours were observed. Collectively our results indicate that developmental eggs exhibit differential and specific time-dependent expression profile of target genes that can contribute as measurable factors in future investigations.