The dorsal region spontaneously developed three layers along the dorsal - ventral axis: the ventricular zone, a Purkinje -
cell precursor zone, and a rhombic lip zone.
His group defined a functional niche for B
cells (around sinusoids in the bone marrow), identified the first two mutants that abrogate marginal
zone B lymphocyte development, developed the concept of a follicular versus marginal
zone B lymphoid
cell - fate decision, and discovered two new defined stages of peripheral B
cell development, the marginal
zone precursor (MZP) B
cell, and the Follicular type II B
cell.