Reorganization of longitudinal compartments in the laterally protruding paraflocculus of the postnatal mouse cerebellum

Abstract

The paraflocculus and the neighboring smaller flocculus form a remarkable protrusion in the ventrolateral aspect of the mouse cerebellum, in which the longitudinal compartments are conspicuously oriented perpendicularly to the sagittal plane. The developmental process of such anatomical arrangements in these lobules has not been fully clarified. Here, we used the genetic tractability of pcdh10‐lacZ knock‐in (OL‐KO), IP 3R1‐nls‐lacZ transgenic (1NM13) and Gpr26cre‐Ai9‐AldocV mice to track the development of compartments and examined local longitudinal orientation of Purkinje cells within the paraflocculus and flocculus. We observed a distinct pcdh10‐positive (pcdh10+) compartment in the flocculus, whereas the paraflocculus and other lobules had a continuous paravermal pcdh10+ compartment, in the embryonic OL‐KO cerebellum. During the first postnatal week, the parafloccular pcdh10+ compartment shifted laterally to the most lateral edge in the caudal part of the protruding paraflocculus. Although the most medial edge of the parafloccular pcdh10+ compartment remained in the nonprotruding part of the paraflocculus, it was disrupted from the originally continuous pcdh10+ compartment in the copula pyramidis. The local longitudinal orientation changed gradually along with the mediolateral extent of the copula pyramidis, almost becoming perpendicular to the sagittal plane in the laterally connected paraflocculus in the adult cerebellum. This rotational change in orientation was derived from the short U‐shaped embryonic cerebellum, in which the surfaces of the flocculus and paraflocculus were oriented laterally. These results indicated that the peculiar compartmental organization of the paraflocculus originates from the embryonic common hemispheric compartmental organization and shaped by the significant reorganization process in the first postnatal week.

Striped Distribution Pattern of Purkinje Cells of Different Birthdates in the Mouse Cerebellar Cortex Studied with the Neurog2-CreER Transgenic Line

“…The paraflocculus has been shown to have a longitudinal compartmental organization equivalent to that of the hemisphere (Panezai et al, 2020). However, the present results showed different distributions of birthdate-specific PCs between the hemisphere and paraflocculus.…”

“…Since cortical longitudinal stripes in the paraflocculus and flocculus are arranged roughly in parallel to the coronal plane (Panezai et al, 2020), horizontal sections were preferentially used to analyze birthdate-specific PC distribution in these lobules. In the paraflocculus, PCs in the caudal part (left side in panels of Fig.…”

“…9A-H). The positional relationship between these areas and molecular compartments of the paraflocculus (Panezai et al, 2020) was not clear yet. In the flocculus, six stripes were observed with different tamoxifen timing.…”

Scaling patterns of cerebellar petrosal lobules in Euarchontoglires: Impacts of ecology and phylogeny

“…The homology of the cerebellar structures that are housed in the subarcuate fossa can vary between orders, which has implications for their nomenclature and how we understand their functions between taxa. In Glires (Panezai et al, 2020; Tan et al, 1995) and Scandentia (Ni et al, 2018) the lobules are formed by the paraflocculi, which are divided into the ventral and dorsal paraflocculus (Tan et al, 1995). In contrast, the petrosal lobules of primates are formed by only a portion of the paraflocculi (Voogd & Barmack, 2006).…”

3D Reconstruction of the Clarified Rat Hindbrain Choroid Plexus

“…In regards to rat hCP macroanatomy, the observed peculiar arrangements of arteries and veins most likely reflect development of the cerebellum and related structures. In fact, the rodent paraflocculus extends laterally, reorients during development, and ends surrounded by temporal bone ( Panezai et al, 2020 ); on the other hand, the dorsal cochlear nucleus is a paracerebellar nucleus that shares a similar (though not identical) developmental origin with the cerebellum ( Farago et al, 2006 ), and therefore association of CP-related vasculature to cochlear nuclei may reflect rhombic lip rearrangements during development.…”