関連する実験動画
Updated: Jul 10, 2026
07:36
C. elegans Tracking and Behavioral Measurement
Published on: November 17, 2012
蛇の無四肢と軸のパターンの発達的基礎
1Division of Zoology, School of Animal and Microbial Sciences, University of Reading, UK. M.J.Cohn@reading.ac.uk
Nature
|June 12, 1999
まとめ
蛇の進化には重要な体型変化が伴いましたが,その発達の起源は不明でした. パイソンの胚におけるホックス遺伝子の拡張は,四肢の喪失と幹の伸びを説明し,重要な進化的メカニズムを明らかにする.
科学分野:
- 発達生物学 発達生物学とは
- 進化生物学の進化生物学について
- 比較解剖学の比較解剖学について
背景:
- 蛇の進化は,手足の喪失と体幹の伸びを含む,脊椎動物の主要な体平面の変化によって特徴付けられています.
- ヘビにおけるこれらの進化的変化の発展的基盤は,ほとんど不明のままである.
- 手足の喪失と幹の伸びを組み合わせると,分類全体に共通する発達メカニズムが示唆される.
研究 の 目的:
- パイソンの胚におけるヘビ特有の体型変化の発達基盤を調査する.
- 前肢の欠如と後肢の縮小におけるホックス遺伝子発現の役割を決定する.
- パイソンの四肢の発達と潜在的な救助メカニズムに関与するシグナル伝達経路を探求する.
主な方法:
- 前後軸に沿ったパイトン胚のホックス遺伝子発現パターンの分析.
- 後肢の芽の開始と,重要な肢体シグナル伝達経路の活性化 (アピカルリッジ,極化領域) の調査.
- ファイブロブラスト成長因子 (FGF) とチキのアピカルリッジ再結合を用いた実験的操作で,パイソンの肢体発達の救出を評価する.
主要な成果:
- 拡張されたホックス遺伝子発現ドメインは,パイトンボディ軸に沿って観察されました.
- このホックス遺伝子の拡張は前肢の欠如と,胸の脊椎同一性の増加と相関しています.
- パイソンの後肢の芽は発芽するが,アピカルリッジと極化領域のシグナル伝達がないために発芽しない.
- パイソンの肢芽の成長とソニック・ヘッジホッグのシグナル伝達は,FGFまたはチキン・アピカル・リッジによって救出することができます.
結論:
- パイソンの胚形成中に変化したホックス遺伝子の発現は,前肢の喪失と軸骨格の伸びの両方の主要な原動力です.
- ピトンにおける四肢芽の発達障害は,重要な四肢信号伝達経路の不調と関連している.
- これらの発達変化は,ホックス遺伝子調節の早期のシフトから発生する可能性があり,ヘビの体プランの進化の洞察を提供します.
関連する概念動画
01:56Gastrulation
Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of intricate cellular movements, which in humans transforms a flat, “bilaminar disc” composed of two cell sheets into a three-tiered structure. In the resulting embryo, the endoderm serves as the bottom layer, and stacked directly above it is the intermediate mesoderm, and then the uppermost ectoderm. Respectively, these tissue strata will form...
01:13Formation of Muscle Fibers from Myoblasts
De novo myogenesis, or the formation of muscle fibers, begins during the early embryonic stages. The skeletal muscle is formed from somites– blocks of embryonic cell layers. The somites are further divided into dermatomes, myotomes, sclerotomes, and syndetomes. Among these, the myotomes give rise to muscle fibers.
Muscle progenitor cells (MPCs) are formed from the myotomes. MPCs express genes that encode the transcription factors Pax3 and Pax7. Along with Pax 3/7, other transcription factors...
Muscle progenitor cells (MPCs) are formed from the myotomes. MPCs express genes that encode the transcription factors Pax3 and Pax7. Along with Pax 3/7, other transcription factors...
01:09Overview of the Axial Skeleton
The skeleton is subdivided into two major divisions—the axial skeleton and the appendicular skeleton. The axial skeleton forms the vertical, central axis of the body. It includes all of the bones of the head, neck, chest, and back. It protects the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back and for muscles that act across the shoulder and hip joints to move their corresponding limbs.
The axial skeleton of the adult...
The axial skeleton of the adult...
01:09Changes in the Appendicular Skeleton with Age
The upper and lower limb initially develops as a small bulge called a limb bud, which appears on the lateral side of the early embryo. The upper limb bud appears near the end of the fourth week of development, with the lower limb bud appearing shortly after.
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
01:07Development of the Limb Synovial Joints
Joints form during embryonic development in conjunction with the formation and growth of the associated bones. The embryonic tissue that gives rise to all bones, cartilage, and connective tissues of the body is called mesenchyme.
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
01:15Development of the Sexual Organs in the Embryo and Fetus
Development of the reproductive organs in an embryo starts from a bipotential state. This means the early embryo can develop either male or female reproductive organs. The formation of these organs begins with the growth of gonadal ridges that arise from the intermediate mesoderm during the fifth week of development.
Near the gonadal ridges, two duct systems are present: the mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts). These ducts form the basis for the male...
Near the gonadal ridges, two duct systems are present: the mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts). These ducts form the basis for the male...