Xenbase Image ID: 175613

Figure 1. Timing, axial patterning, and time-space translation. Above: The structure of the vertebrate A–P axis: domains with significant Hox genes and other markers. An unexpected element is introduced by the newly characterized extreme anterior domain (EAD), which makes the face. This is shown as the most anterior part of the straight axis. Actually, the anterior end of the dorsal A–P axis bends backward around to the ventral side of the embryo to face posteriorly like the handle of a walking stick (not shown). A. Head: anterior head (corresponding to telencephalon, diencephalon, mesencephalon). P. Head: posterior head (corresponding to anterior rhombencephalon, occipital somites). Neck: cervical somites, posterior rhombencephalon, Thorax: thoracic vertebrae, anterior spinal cord. Abdomen: Lumbar and sacral regions, spinal cord. Tail: coccygeal vertebrae, spinal cord. Above and below: Time space translation. A biological timer, represented by the clock face below, proceeds from 1 to 12 (red numbers). The timer starts with information needed for making the EAD, proceeds to the anterior head, then to posterior head, then to neck, then to thorax, then abdomen, then tail. The timer needs BMP to function, so occurs in tissues with high BMP (yellow/orange). Anti–BMP factors (blue) interact with the timer sequentially to freeze the identities of an A–P sequence of axial zones. In the axial sequence, the Hox genes are each both a component of the timer at their appropriate times and are sequentially involved in setting up the A–P sequence of axial zones. The genes involved in time space translation in the EAD‐head zones are unknown. The head and tail of the A–P timer are close together because of their representation on a clock face. No statement about molecular identities is intended. Image published in: Durston AJ (2019) © 2019 The Author. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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