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Morphogenesis and Molecular Regulation of Colour Patterning in Birds

Periodic Reporting for period 4 - COLOUR PATTERN (Morphogenesis and Molecular Regulation of Colour Patterning in Birds)

Reporting period: 2019-11-01 to 2020-04-30

Our laboratory focuses on the processes of formation and evolution of natural patterns (i.e. visible arrangement of characters across bodies and tissues). A major challenge has been to understand how patterns can arise from initially homogeneous structures in a reproducible manner, while allowing apparent complexity and diversity. We set to identify molecules acting as positional cues, characterise the morphogenetic response (cell / tissue rearrangements) to these cues, and how such pattern-forming processes constrain (or promote) the evolution of natural patterns. We use natural variation, mathematical modelling and experimental tests in vivo. We take advantage of the color and feather pattern of birds.
Aim1: Characterise color pre-pattern formation and the source of positional cues forming large color domains
We showed in Estrildid finches that color pattern diversity is limited by an embryonic "paintbox", resulting from shared developmental pathways and patterning events.
This work is in preparation for publication in 2020.

Aim2: Identify the molecular events establishing the pre-pattern of large color domains.
We have identified several candidate pathways and currently work to investigate the function of these candidates through CRISPr-Cas9 mediated gene editing

Aim3: Characterisation of stripe patterning dynamics
We have shown that periodic stripes of Galliformes result from a combination of instructive signalling from the somite and local dose-dependent events mediated by the agouti pigmentation gene. This work has been published in the journal Science in 2018.
We have shown that sequential feather patterning in poultry, ratites and penguin birds is triggered by initial conditions in the naïve skin and requires a combination of local proliferation and self-organisation mechanisms. This work has been published in the journal PLoS Biology in 2019.

Aim4: Characterisation of stripe patterning evolution.
We have identified factors shaping the formation of strupe diversity in Galifformes (see Aim 3) and ratites. We currently work to investigate through both numerical modelling and empirical studies the embryonic origin of positional signals for multi-striped birds.
Our work has so far provided important advances to the state of the art by showing that:
- Large colour domains result from the coordinated expression of developmental genes in a timely fashion (Aim 1 and 2)
- Periodic patterns result from both early developmental landmarks that constrain their evolution and local dynamics occurring late within developing tissues (Aim 3 and 4)
- Colour and skin patterns are triggered by initial conditions present in the naive skin and relayed by the progression of competence fronts (Aim 3)
- Diversity in colour and skin pattern is largely linked to morphogenetic events and biophysical mechanics in the cutaneous tissue (Aim 3 and 4)