Academic Background

B.A., Macalester College, MN, 1987
Ph.D., Stanford University, CA, 1993

Gene expression in embryogenesis

Formation of the vertebrate central nervous system (CNS) begins early during embryogenesis - at gastrula stages, but extensive refinements continue to take place before the fully functional adult CNS emerges. Neural development is carefully controlled and perturbations of this process give rise to defects ranging from severe developmental abnormalities to mild cognitive impairments. We are studying genes that control early neural development, particularly formation of the caudal CNS (hindbrain and spinal cord) in the zebrafish, using a three-step strategy. 

Gene discovery
We are screening for novel genes involved in neural development by several approaches.  First, we have used subtractive hybridization to isolate genes expressed specifically in the caudal CNS. Second, we are using ‘expression profiling’ to identify novel genes expressed downstream of paralog group 1 hox genes in the caudal hindbrain.  Third, we are undertaking a haploid genetic screen for mutations affecting hindbrain development. 

Derive genetic pathways
We next integrate these genes into pathways that drive hindbrain development, using a number of molecular genetic approaches. For instance, we use injection of synthetic mRNA to ectopically activate gene function in wild type embryos, or to rescue defects in various mutant lines, and we use antisense technology to ‘knock-down’ the function of specific genes. In addition, we have recently adapted the Gal4:UAS transgenic system to achieve tissue specific expression of transgenes within the developing hindbrain.

Define biochemical activities
Lastly, we define the function of the various gene products using a variety of biochemical approaches.  Since the majority of the genes we identified turn out to act as transcription factors (pbx4, meis3, hoxb1b, hoxb1a, nlz1, nlz2), we have used ChIP to assay binding of these factors to target promoters in zebrafish embryos. Similarly, we have used ChIP to detect changes in histone modifications mediated by these transcription factors at specific promoters. Furthermore, several of the hindbrain specific genes we identified appear to act as protein phosphatases and we are currently attempting to identify their substrates both in zebrafish embryos and in cell culture systems.

Research Figure

Legend:

Wholemount in situ hybridization detects the expression of four different genes (two in red, two in purple) in the forming neurectoderm of the zebrafish. (Dorsal view at 10 hours post fertilization.)