You are doing a newborn exam and find a baby with narrow, sloping, "weird" shoulders. The baby seems unusually flexible; you can bring his shoulders almost together in the midline in front. You identify the abnormality on the CXR above. You remember that this diagnosis often involves delayed closing of the fontanelles (which may remain open to adulthood), defective bone formation, short stature, supernumerary teeth, and abnormal tooth eruption.
Challenge: The defective gene is a transcription factor called what?
Hint: The number of ribs you count isn't important, but you may notice something interesting while counting the ribs.
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