An exercise in brain genoarchitectonics: Analysis of AZIN2‐Lacz expressing neuronal populations in the mouse hindbrain

Abstract

We examined in detail the distribution of AZIN2 (antizyme inhibitor 2) expression in the adult mouse hindbrain and neighboring spinal cord. AZIN2, similar to previously known AZIN1, is a recently-discovered, a functional paralog of ornithine decarboxylase (ODC). Due to their structural similarity to ODC, both AZIN1 and AZIN2 counteract the inhibitory action of 3 known antizymes (AZ1-3) on the ODC synthesis of polyamines, thus increasing intracytoplasmic levels of polyamines. AZIN2 is strongly, but heterogeneously, expressed in the brain. Our study uses a mouse line carrying an AZIN2-LacZ construct, and, in our topographic analysis of AZIN2-positive structures, we intend to share new knowledge about the rhombomeric segmentation of the hindbrain (a function of Hox paralogs and other genes). The observed labeled cell populations predominantly coincide with known cholinergic and glutamatergic cells, but occasionally also correspond to GABAergic, and possibly glycinergic cells. Some imperfectly known hindbrain populations stood out in unprecedented detail, and some axonal tracts were also differentially stained. © 2017 Wiley Periodicals, Inc.

Concentric ring topology of mammalian cortical sectors and relevance for patterning studies

“…The procedures we follow for ISH performed on floating sections, with immunoreaction as a counterstain or not, were published in Ferran et al (). Methodological data for transgenic Azin2‐LacZ material were reported in Martinez‐de‐la‐Torre, Lambertos, Peñafiel, and Puelles ().…”

“…We further show, in Figure b, a cross‐section through the adult mouse telencephalon, illustrating a sharply differential pattern of Azin2 ‐LacZ signal and parvalbumin (PV) immunoreactive counterstaining in the neocortex versus insular mesocortex. Azin2 codes for a protein that regulates ornithine‐decarboxylase in the synthesis of polyamines; Azin2 protein is selectively present postnatally in a variety of brain cell populations, including cortical ones (see Martinez‐de‐la‐Torre et al, , also for details of the mouse strain used for this material). It is clear at first glance that Azin2‐LacZ signal shows a rather different insular mesocortical pattern than in neocortical layers (compare this insular lamination pattern with that of Rprm recorded in figure 4.15A of Puelles, ).…”

Segmental Analysis of the Vestibular Nerve and the Efferents of the Vestibular Complex

“…In previous fate maps of the avian hindbrain, a rhombomeric extension of the vestibular column from r1 to r10 (Marín and Puelles, ; Cambronero and Puelles, ) was proposed, according to quail‐chick grafting experiments. However, recent data suggest, at least in mice, the vestibular nuclei start at r2, caudal to the end of the locus coeruleus and mesencephalic trigeminal nucleus, both located at r1 (Martinez‐de‐la‐Torre et al, ).…”

The Postmigratory Alar Topography of Visceral Cranial Nerve Efferents Challenges the Classical Model of Hindbrain Columns

“…Ju et al ()'s result that visceral efferents of mixed nerves move into the molecularly defined alar plate clearly forces anatomic reinterpretation (or aban donment) of the classic hindbrain columnar model (Puelles, ; plate 57 in Nieuwenhuys and Puelles, ; Martínez‐de‐la‐Torre et al, ). Most experts in the field have not yet reacted to this new scenario, essentially because of the enormous dogmatic weight of the classic columnar model, which silently demands unparsimonious efforts to conciliate any contradictory result with it.…”