New method to deliver exogenous material into developing planarian embryos

Abstract

The ability to report or modify the embryological processes in living embryos is pivotal for developmental biology research. Planarian embryology has experienced renewed interest as the genetic pathways that drive adult regeneration were found to be involved in the development of embryos. The major drawback to the study of planarian embryology is the absence of methods that give access to the embryos and enable their manipulation. Herein, we report on a novel method for delivering external material into developing embryos using nanosecond laser pulses. When focused on the eggshell surface under optimal parameters, laser pulses ablate the protective case and open a pathway throughout which foreign material can be delivered. In this study, we used egg capsules from Schmidtea polychroa (Schmidt, 1861) to microinject 1 microm fluorescein isothiocyanate fluorescent beads into the live embryos. We obtained viability values ranging from 15% in early egg capsules to 100% in late developmental stages. Moreover, we measured the delivery effectiveness as the number of hatchlings containing fluorescent beads per microinjected egg capsule, reaching 100% in early stages and almost 40% in late stages. This is the first time that planarian embryos have been modified without compromising normal development. We consider that this technique will be of extreme value to future work on planarian developmental biology and regeneration, enabling the application of modern functional tools to the study of this Lophotrochozoan.

The mid-developmental transition and the evolution of animal body plans

“…A population of S. polychroa was maintained in the lab at 20°C as previously described 32 . Egg capsules were regularly collected over 15 days of development just after deposition and kept in Petri dishes at 20°C.…”

Genetic dissection of the planarian reproductive system through characterization of Schmidtea mediterranea CPEB homologs

“…4A). These capsules are filled by hundreds of yolk cells that nurture the developing embryo (Martin-Duran et al, 2008; Shinn, 1993). Upon deposition, capsules undergo a “quinone tanning” process in which the proteinaceous shell hardens and darkens from yellow to dark-brown hues (Fig.…”

Spoltud-1 is a chromatoid body component required for planarian long-term stem cell self-renewal

“…S. polychroa is convenient in order to study embryonic development and provides the possibility of comparing regeneration data to available embryonic development data (Martin-Duran et al, 2008; Solana and Romero, 2009). Furthermore, this species is closely related to S. mediterranea , for which there is an ongoing genome project.…”