Sen-Lin Lai | PubMed Health

PubMed2006

Genetic mosaic with dual binary transcriptional systems in Drosophila.

MARCM (mosaic analysis with a repressible cell marker) involves specific labeling of GAL80-minus and GAL4-positive homozygous cells in otherwise heterozygous tissues. Here we demonstrate how the concurrent use of two independent binary transcriptional systems may facilitate complex MARCM studies in the Drosophila nervous system. By fusing LexA with the VP16 acidic activation domain (VP16) or the GAL4 activation domain (GAD), we obtained both GAL80-insensitive and GAL80-suppressible transcriptional factors. LexA::VP16 can mediate MARCM-independent binary transgene induction in mosaic organisms. The incorporation of LexA::GAD into MARCM, which we call dual-expression-control MARCM, permits the induction of distinct transgenes in different patterns among GAL80-minus cells in mosaic tissues. Lineage analysis with dual-expression-control MARCM suggested the presence of neuroglioblasts in the developing optic lobes but did not indicate the production of glia by postembryonic mushroom body neuronal precursors. In addition, dual-expression-control MARCM with a ubiquitous LexA::GAD driver revealed many unidentified cells in the GAL4-GH146-positive projection neuron lineages.

Animals↗

PubMed2006

Automatic 3-D grayscale volume matching and shape analysis.

Recently, shape matching in three dimensions (3-D) has been gaining importance in a wide variety of fields such as computer graphics, computer vision, medicine, and biology, with applications such as object recognition, medical diagnosis, and quantitative morphological analysis of biological operations. Automatic shape matching techniques developed in the field of computer graphics handle object surfaces, but ignore intensities of inner voxels. In biology and medical imaging, voxel intensities obtained by computed tomography (CT), magnetic resonance imagery (MRI), and confocal microscopes are important to determine point correspondences. Nevertheless, most biomedical volume matching techniques require human interactions, and automatic methods assume matched objects to have very similar shapes so as to avoid combinatorial explosions of point. This article is aimed at decreasing the gap between the two fields. The proposed method automatically finds dense point correspondences between two grayscale volumes; i.e., finds a correspondent in the second volume for every voxel in the first volume, based on the voxel intensities. Mutiresolutional pyramids are introduced to reduce computational load and handle highly plastic objects. We calculate the average shape of a set of similar objects and give a measure of plasticity to compare them. Matching results can also be used to generate intermediate volumes for morphing. We use various data to validate the effectiveness of our method: we calculate the average shape and plasticity of a set of fly brain cells, and we also match a human skull and an orangutan skull.

Algorithms↗