Developmental origin of tendon diversity in .

Myogenesis is a developmental process that is largely conserved in both and higher organisms. Consequently, the fruit fly is an excellent model for identifying the genes and mechanisms involved in muscle development. Moreover, there is growing evidence indicating that specific conserved genes and signaling pathways govern the formation of tissues that connect the muscles to the skeleton.

Activation of the ubiquitin-proteasome system contributes to oculopharyngeal muscular dystrophy through muscle atrophy.

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset disorder characterized by progressive weakness and degeneration of specific muscles. OPMD is due to extension of a polyalanine tract in poly(A) binding protein nuclear 1 (PABPN1). Aggregation of the mutant protein in muscle nuclei is a hallmark of the disease.

Transcriptomic and Genetic Analyses Identify the Krüppel-Like Factor Dar1 as a New Regulator of Tube-Shaped Long Tendon Development.

To ensure locomotion and body stability, the active role of muscle contractions relies on a stereotyped muscle pattern set in place during development. This muscle patterning requires a precise assembly of the muscle fibers with the skeleton via a specialized connective tissue, the tendon. Like in vertebrate limbs, leg muscles make connections with specific long tendons that extend through different segments.

MACF1 controls skeletal muscle function through the microtubule-dependent localization of extra-synaptic myonuclei and mitochondria biogenesis.

Skeletal muscles are composed of hundreds of multinucleated muscle fibers (myofibers) whose myonuclei are regularly positioned all along the myofiber's periphery except the few ones clustered underneath the neuromuscular junction (NMJ) at the synaptic zone. This precise myonuclei organization is altered in different types of muscle disease, including centronuclear myopathies (CNMs). However, the molecular machinery regulating myonuclei position and organization in mature myofibers remains largely unknown.

Muscle development : a view from adult myogenesis in Drosophila.

In Drosophila the first wave of myogenesis occurs in the embryo to produce the larval muscles. This musculature undergoes histolysis and largely disappears during metamorphosis, while a second wave of myogenesis begins to generate the muscles of the adult fly. The core myogenic program is highly conserved among both invertebrate and vertebrate species, and Drosophila embryogenic myogenesis is a well-recognized model for identifying genes and pathways governing muscle development.

Odd-skipped and Stripe act downstream of Notch to promote the morphogenesis of long appendicular tendons in .

Multiple tissue interactions take place during the development of the limb musculoskeletal system. While appendicular myogenesis has been extensively studied, development of connective tissue associated with muscles has received less attention. In the developing leg, tendon-like connective tissue arises from clusters of epithelial cells that invaginate into the leg cavity and then elongate to form internal tube-shape structures along which muscle precursors are distributed.

Characterization of Drosophila Muscle Stem Cell-Like Adult Muscle Precursors.

Uncovering how muscle stem cells behave in quiescent and activated states is central to understand the basic rules governing normal muscle development and regeneration in pathological conditions. Specification of mesodermal lineages including muscle stemlike adult muscle precursors (AMPs) has been extensively studied in Drosophila providing an attractive framework for investigating muscle stem cell properties. Restricted number of AMP cells, relative ease in following their behavior, and large number of genetic tools available make fruit fly an attractive model system for studying muscle stem cells.

Coordinated Development of Muscles and Tendon-Like Structures: Early Interactions in the Drosophila Leg.

The formation of the musculoskeletal system is a remarkable example of tissue assembly. In both vertebrates and invertebrates, precise connectivity between muscles and skeleton (or exoskeleton) via tendons or equivalent structures is fundamental for movement and stability of the body. The molecular and cellular processes underpinning muscle formation are well-established and significant advances have been made in understanding tendon development.

The conserved transcription factor Mef2 has multiple roles in adult Drosophila musculature formation.

Muscle is an established paradigm for analysing the cell differentiation programs that underpin the production of specialised tissues during development. These programs are controlled by key transcription factors, and a well-studied regulator of muscle gene expression is the conserved transcription factor Mef2. In vivo, Mef2 is essential for the development of the Drosophila larval musculature: Mef2-null embryos have no differentiated somatic muscle.

The Him gene inhibits the development of Drosophila flight muscles during metamorphosis.

During Drosophila metamorphosis some larval tissues escape the general histolysis and are remodelled to form adult tissues. One example is the dorso-longitudinal muscles (DLMs) of the indirect flight musculature. They are formed by an intriguing process in which residual larval oblique muscles (LOMs) split and fuse with imaginal myoblasts associated with the wing disc.

Shaping leg muscles in Drosophila: role of ladybird, a conserved regulator of appendicular myogenesis.

Legs are locomotor appendages used by a variety of evolutionarily distant vertebrates and invertebrates. The primary biological leg function, locomotion, requires the formation of a specialised appendicular musculature. Here we report evidence that ladybird, an orthologue of the Lbx1 gene recognised as a hallmark of appendicular myogenesis in vertebrates, is expressed in leg myoblasts, and regulates the shape, ultrastructure and functional properties of leg muscles in Drosophila.

Coordinated development of muscles and tendons of the Drosophila leg.

Since Miller's morphological description, the Drosophila leg musculature and its formation has not been revisited. Here, using a set of GFP markers and confocal microscopy, we analyse Drosophila leg muscle development, and describe all the muscles and tendons present in the adult leg. Importantly, we provide for the first time evidence for tendons located internally within leg segments.

The ink4a/arf locus evolution in primates: characterization of three ARF sequences.

The human ink4a/arf locus encodes two cell cycle regulatory proteins - the cyclin-dependent kinase inhibitor (p16(ink4a)), and the p53 activator (ARF) - through the use of alternative first exons. This genomic organization is unique in eukaryotes, with two different proteins obtained using different reading frames. The divergence between mouse or opossum and human ARF is very high, whereas proteins have the same nucleolar localization and function.