Introduction: Where Does Growth and Form Originate?

• Cells in an embryo work together like ingredients in a recipe to build a complex body.
• Traditionally, genes have been seen as the main instructions (the “chef”), but extra-genomic signals also help guide development.
• These external signals come from both physical (abiotic) and biological sources.

Physical (Abiotic) Influences on Patterning

• Geomagnetic Field:
  • The Earth’s magnetic field acts like a giant invisible magnet that can affect how organisms develop.
  • Experiments show that shielding from this field can cause defects—imagine missing a key ingredient in a recipe.
• Temperature:
  • Temperature functions like an oven’s setting, influencing how quickly and in what way development proceeds.
  • Different temperatures can change body segment numbers or even affect sex determination in some species.
• Light:
  • Light exposure guides the formation of structures, much like sunlight helps plants grow.
  • Both too much and too little light can alter development, similar to overcooking or undercooking food.
• Water and Nutrient Content (in Plants):
  • Soil composition and water availability influence how plant roots develop, just as the quality of ingredients affects a dish.
  • Plants adjust their root systems to optimize nutrient uptake based on the soil’s makeup.
• Diet (in Animals):
  • Nutrition affects body proportions; poor diet may lead to smaller or misshapen organs.
  • Just like following a recipe requires the right amount of ingredients, proper nutrition is essential for normal development.

Biological Influences on Pattern Determination

• Organism Density:
  • The number and closeness of individuals or cells can change developmental outcomes, similar to how crowded conditions affect group behavior.
  • For example, some fish change sex based on the number of neighbors, and locusts change color when crowded.
• Parasites and Commensals:
  • Microorganisms living with an organism can influence its development.
  • This is like having helpful or harmful assistants that alter the “recipe” for body formation.
• Predators and Prey:
  • The presence of predators can trigger defensive changes, similar to a chef adjusting a recipe for a special occasion.
  • Prey species may develop protective shapes or behaviors to avoid being eaten.
• Uterine Position/Conditions:
  • The location of an embryo in the uterus can affect its growth, much like different spots in an oven can lead to uneven baking.
  • This can influence size, hormone levels, and future behavior.

Mechanisms Behind These Influences

• Chromatin State:
  • Chromatin is the combination of DNA and proteins that controls which genes are active—imagine it as a cookbook that decides which recipes to use.
  • Modifications to chromatin (like making notes on a cookbook) can turn genes on or off and thus influence development.
• Cytoskeleton and Cortical Inheritance:
  • The cytoskeleton is the cell’s internal framework, similar to scaffolding in a building, which helps maintain shape and directs movement.
  • It also passes structural information from one cell generation to the next.
• Biomechanics:
  • Mechanical forces such as pressure and tension help shape tissues, much like kneading dough changes its texture.
  • Proper distribution of these forces is essential for organs and tissues to form correctly.
• Non-neural Bioelectrics:
  • Cells use electrical signals (similar to tiny batteries) even outside of the nervous system to communicate.
  • These bioelectric signals help guide cells on where and how to form specific body parts.

Conclusion

• Both genetic instructions and extra-genomic signals (from physical and biological sources) work together to shape body structure and function.
• This process is like following a complex recipe where every ingredient and step matters.
• Understanding these influences can improve regenerative medicine and provide insights into evolution and development.

观察与形态发生：外基因指导信号综述 (中文)

• 引言：生长与形态的控制来源
  • 胚胎中的细胞像按照菜谱合作的食材，共同构建一个复杂的身体。
  • 传统上，基因被视为主要的指导者，但基因外的信号也在指导发育。
  • 这些外部信号既来自物理（非生物）因素，也来自生物因素。

物理（非生物）因素对形态的影响

• 地磁场：
  • 地球的磁场像一个巨大的无形磁铁，对生物发育有影响。
  • 屏蔽地磁场可能导致发育缺陷，就好比在做菜时缺少了关键的原料。
• 温度：
  • 温度就像烤箱的温度设定，决定了发育的速度和方式。
  • 不同温度可以改变身体的分节数，甚至在某些物种中影响性别的决定。
• 光照：
  • 光照指导结构的形成，就如同阳光帮助植物生长一样。
  • 光照过强或过弱都可能改变发育结果，类似于食物烹饪时火候不当。
• 水分与营养（植物）：
  • 土壤的组成和水分供应影响植物根系的发育，就像原料的质量决定了一道菜的成败。
  • 植物会调整根系结构以更好地吸收养分。
• 饮食（动物）：
  • 营养状况会影响身体比例；营养不良可能导致器官变小或形状异常。
  • 正如烹饪需要恰当的食材比例，正常发育也需要充足的营养支持。

生物因素对形态决定的影响

• 个体密度：
  • 个体或细胞的数量和距离会影响发育结果，就像人多时行为会发生变化。
  • 例如，某些鱼类会根据周围同伴的数量改变性别，蝗虫在拥挤时颜色会改变。
• 寄生生物与共生体：
  • 生活在体内或体外的微生物能影响宿主的发育。
  • 这些微生物有时像友好的助手，有时则像入侵者，改变发育“菜谱”。
• 捕食者与猎物：
  • 捕食者的存在会触发防御性变化，类似于厨师为应对特殊情况而调整菜谱。
  • 猎物物种会在捕食者出现时发展出保护性的形态或行为。
• 子宫位置与条件：
  • 胚胎在子宫中的位置会影响其发育，就像在烤箱中不同位置可能导致烘焙不均。
  • 这可能影响胚胎的体型、激素水平甚至未来的行为模式。

调控机制

• 染色质状态：
  • 染色质由DNA和蛋白质组成，控制基因的活跃程度，就像一本决定菜谱的烹饪书。
  • 对染色质的修饰（就像在书上做记号）可以开启或关闭特定基因，从而影响发育。
• 细胞骨架与皮质遗传：
  • 细胞骨架是细胞内部的支架，帮助维持形状并引导细胞运动，就像建筑中的脚手架。
  • 它还能传递结构信息给后代细胞，确保形态的一致性。
• 生物力学：
  • 机械力（如压力和拉力）帮助塑造组织，就像揉面团会改变面团的质感一样。
  • 正确分布的力对器官和组织的正常形成至关重要。
• 非神经生物电：
  • 细胞利用电信号进行交流，即使不在神经系统中，也像微小电池一样传递信息。
  • 这些生物电信号帮助指导细胞何时何地构建特定的身体部位。

结论

• 基因指令与来自外部的物理和生物信号共同决定了身体的形态和功能。
• 这一过程就像遵循一份复杂的菜谱，每个步骤和原料都不可或缺。
• 对这些影响的深入理解有助于推动再生医学的发展，并为我们提供全新视角理解进化与发育。