Ralf Spörle

Computer-based three-dimensional visualization of developmental gene expression.

A broad understanding of the relationship between gene activation, pattern formation and morphogenesis will require adequate tools for three-dimensional and, perhaps four-dimensional, representation and analysis of molecular developmental processes. We present a novel, computer-based method for the 3D visualization of embryonic gene expression and morphological structures from serial sections. The information from these automatically aligned 3D reconstructions exceeds that from single-section and whole-mount visualizations of in situ hybridizations. In addition, these 3D models of gene-expression patterns can become a central component of a future developmental database designed for the collection and presentation of digitized, morphological and gene-expression data. This work is accompanied by a web site (http://www.univie.ac.at/GeneEMAC).

System to identify individual somites and their derivatives in the developing mouse embryo.

The identification of the axial levels of metameric elements along the rostro‐caudal axis of vertebrates until now was not possible before late, fetal development, when the vertebral anlagen first appear. We developed a new system for the exact axial identification of somites and their derivatives from early, embryonic stages of mouse development on (Theiler stages (TS) 15 to TS18‐19). The initial axial identification of the somites was performed by relating them to the rostral‐most two cervical spinal ganglia (SG), that exhibited characteristic morphologies (SG‐C1: bar‐like, SG‐C2: triangular). At all stages of somitic development, the most prominent somite along the rostro‐caudal axis correlated with the bar‐like SG‐C1, and, therefore, we named it the first cervical somite (SO‐C1). The next step, the axial identification of the somites independently from the SG, was based on the observation that after in situ hybridization to Myf5, Pax3, Pax1, and Mox1 riboprobes, a distinct and characteristic morphology of the last occipital somite (SO‐O5) and the first two cervical somites (SO‐C1, SO‐C2) can be observed. From TS15 on, these three somites formed a triad of the most prominent somites along the rostro‐caudal axis. Also, the dermomyotomal, myotomal, and sclerotomal derivatives of this somite triad were the most prominent in later somitic development. Furthermore, SG‐C1 and SG‐C2 exhibited a transient bipartite anlagen in their early development, suggesting a “resegmentation” during SG formation. Later, when somites started to dissolve, the caudal moiety of the bar‐like SG‐C1 anlagen fused to the anlagen of SG‐C2. Dev. Dyn. 1997;210:216–226.

Neural tube morphogenesis

Many important findings in the past year have helped to identify multiple cellular interactions and signals in vertebrates that govern induction of neuroectoderm, its patterning, neural tube formation, and the subsequent differentiation of neurons. For example, the neural inducers have been shown to function as inhibitors of BMP signaling, the roles of bone morphogenetic proteins and Sonic hedgehog during dorso-ventral specification of the neural tube have been further elucidated and the realization of a dorso-ventral inversion of the body axis contributed to a better understanding of evolutionarily related genes and functions between vertebrates and invertebrates.

The open brain (opb) mutation maps to mouse chromosome 1

The mouse open brain (opb) mutation represents an autosomal recessive mutation with full penetrance of the phenotype. At early stages of development, homozygous mutant embryos exhibit defects in development of the neural tube, spinal ganglia, epaxial muscle, eyes, and limbs (Gtinther et al. 1994; Sp6rle et al. 1996). Here, we describe neural tube and vertebral column defects resulting in spina bifida at later developmental stages, and we report on the mapping of the opb mutation to the proximal region of mouse Chromosome (Chr) 1. The analysis of mouse mutants represents a powerful approach to understand the genetics and etiology of human congenital diseases. In humans, neural tube defects are a major cause of fetal loss, infant mortality, and mental retardation. Among the neural tube defects, spina bifida occurs in 1 3 per 1000 total births (Darling 1996). Spina bifida (characterized by dorsally open neural