Nearly every mammalian cell division is accompanied by a mutational event that becomes fixed in a daughter cell. When carried forward to additional cell progeny, a clone of variant cells can emerge. As a result, mammals are complex mosaics of clones that are genetically distinct from one another. Recent high-throughput sequencing studies have revealed that mosaicism is common, clone sizes often increase with age and specific variants can affect tissue function and disease development. Variants that are acquired during early embryogenesis are shared by multiple cell types and can affect numerous tissues. Within tissues, variant clones compete, which can result in their expansion or elimination. Embryonic mosaicism has clinical implications for genetic disease severity and transmission but is likely an under-recognized phenomenon. To better understand its implications for mosaic individuals, it is essential to leverage research tools that can elucidate the mechanisms by which expanded embryonic variants influence development and disease.

几乎每次哺乳动物细胞分裂都伴随着固定在子细胞中的突变事件。当转移到其他细胞后代时，就会出现变异细胞的克隆。因此，哺乳动物是一种复杂的克隆体镶嵌体，它们在基因上彼此不同。最近的高通量测序研究表明，嵌合现象很常见，克隆大小通常随着年龄的增长而增加，并且特定的变异会影响组织功能和疾病的发展。在早期胚胎发生过程中获得的变异由多种细胞类型共享，并且可以影响许多组织。在组织内，变异克隆竞争，这可能导致它们的扩增或消除。胚胎嵌合现象对遗传病的严重程度和传播具有临床意义，但可能是一种未被充分认识的现象。为了更好地理解它对嵌合体个体的影响，有必要利用研究工具来阐明扩大的胚胎变异影响发育和疾病的机制。