Identification of Mushroom body miniature, a zinc-finger protein implicated in brain development of Drosophila

Abstract

The mushroom bodies are bilaterally arranged structures in the protocerebrum of Drosophila and most other insect species. Mutants with altered mushroom body structure have been instrumental not only in establishing their role in distinct behavioral functions but also in identifying the molecular pathways that control mushroom body development. The mushroom body miniature 1 (mbm 1 ) mutation results in grossly reduced mushroom bodies and odor learning deficits in females. With a survey of genomic rescue constructs, we have pinpointed mbm 1 to a single transcription unit and identified a single nucleotide exchange in the 5 untranslated region of the corresponding transcript resulting in a reduced expression of the protein. A daptive behavior of animals and humans requires functional neuronal circuits in the brain. The genetic programs that control the generation of these circuits by providing an adequate number of neurons, establishing neuronal connectivity, and remodeling them during development and in response to external stimuli during adulthood are just beginning to emerge. The mushroom bodies (MBs), a prominent neuropil structure of the insect brain (1), have become an attractive model system to study many aspects of this intricate network. Functional studies have established a role of the MBs in olfactory learning and memory, controlling locomotor activity, performing visual context generalization, and decision making (2, 3). On the other hand, the structural organization and the development of the MBs have been described in great detail in refs. 4-10. In the adult fly Drosophila melanogaster, Ϸ2,500 intrinsic neurons (Kenyon cells) build up one MB. The Kenyon cell bodies are located in the dorsal cortex and extend their dendritic branches into the calyx, where prominent inputs from other brain regions are received. The Kenyon cell axons fasciculate in the peduncle and extend rostroventral, where most of them bifurcate to form a system of medially and dorsally projecting lobes. Each MB arises from a group of four apparently equipotent neuronal stem cells (neuroblasts), each of which generates in a sequential manner several types of Kenyon cells during larval and pupal stages. MB ␥ neurons are born before the mid-third-larval instar, then ␣Ј͞␤Ј neurons are born, and finally the ␣͞␤ neurons are added at pupal stages (6,8). The nomenclature of the Kenyon cells refers to the corresponding dorsally and medially projecting MB lobes in the adult fly (see Fig. 2). More recently, immunohistochemical studies have identified additional subtypes of Kenyon cells (9). Yet, the anatomical description disregards the structural plasticity of the adult MBs as a consequence of changes in living conditions and experience (11). Furthermore, Kenyon cell axons and dendrites undergo massive remodeling during metamorphosis to establish adult-specific branching patterns. The axons of the ␥ neurons, which bifurcate in a dorsal and a medial branch in the larvae, degenerate and regrow only in the medial direction (8,10,(12)(13)(14).What...

ThensdCGene Encoding a Putative C2H2-Type Transcription Factor Is a Key Activator of Sexual Development inAspergillus nidulans

“…However, unlike other known transcription factors carrying the C 2 H 2 zinc finger, NsdC possesses an additional C 2 HC motif comprising 80 amino acid residues that is highly conserved in various fungal species ( Figure 1B). The C 2 HC motif is found in various eukaryotic proteins that have diverse functions such as chromatin acetylation (Akhtar and Becker 2001;Smith et al 2005), DNA repair ( Jones et al 1988), and development control (Raabe et al 2004;Xie et al 2005). Many C 2 HC motifs bind to DNA (Lee et al 1998;Simpson et al 2003) or interact with motifs of other transcription factors (Sadowski et al 2003).…”

Drosophila Mbm Is a Nucleolar Myc and Casein Kinase 2 Target Required for Ribosome Biogenesis and Cell Growth of Central Brain Neuroblasts

“…The transfection procedure for Western blots was essentially the same, except that 5 ϫ 10 6 S2 cells were transfected with 10 g dsRNA in single wells of a 6-well plate. Samples for Western blots were harvested and further processed according to standard procedures, using rabbit anti-Mbm (1:160) (22), mouse anti-Myc (1:50) (30), and mouse anti-␣-tubulin (1:5,000) (Sigma) antibodies for enhanced chemiluminescence (ECL) detection. For proliferation assays, a CellTrace CFSE cell proliferation kit (Molecular Probes) was used.…”

“…Homology searches provided no clue about the molecular function of Mbm. Structural features of Mbm include several stretches enriched in certain amino acids, a putative nuclear localization signal, and two consecutive CCHC zinc knuckles (22). In this report, we describe Mbm as a new nucleolar protein.…”

“…One of the Myc-responsive genes with an unknown function was mushroom body miniature (mbm). The original hypomorphic mbm 1 allele was identified in a screen for viable structural brain mutants and showed a pronounced reduction in the size of the adult mushroom body neuropil, which was due at least in part to a reduction in the number of intrinsic mushroom body neurons (21,22). More severe allelic combinations indicated a general requirement for Mbm in brain development and uncovered a neuroblast proliferation defect as a major cause of the phenotype.…”

Differential Effects of Tau on the Integrity and Function of Neurons Essential for Learning in Drosophila

“…To verify these initial observations, we used the anti-Leo antibody, which is highly preferential for most adult MB neurons (Skoulakis and Davis, 1996;Crittenden et al, 1998;Raabe et al, 2004). Serial sections from heads of htau 0N4R -expressing animals from independent crosses revealed that all brains displayed defective MBs (Fig.…”