Cortical RORβ is required for layer 4 transcriptional identity and barrel integrity

Abstract

Retinoic acid-related orphan receptor beta (RORβ) is a transcription factor (TF) and marker of layer 4 (L4) neurons, which are distinctive both in transcriptional identity and the ability to form aggregates such as barrels in rodent somatosensory cortex. However, the relationship between transcriptional identity and L4 cytoarchitecture is largely unknown. We find RORβ is required in the cortex for L4 aggregation into barrels and thalamocortical afferent (TCA) segregation. Interestingly, barrel organization also degrades with age in wildtype mice. Loss of RORβ delays excitatory input and disrupts gene expression and chromatin accessibility, with down-regulation of L4 and up-regulation of L5 genes, suggesting a disruption in cellular specification. Expression and binding site accessibility change for many other TFs, including closure of neurodevelopmental TF binding sites and increased expression and binding capacity of activity-regulated TFs. Lastly, a putative target of RORβ, Thsd7a, is down-regulated without RORβ, and Thsd7a knock-out alone disrupts TCA organization in adult barrels.

An allelic series of spontaneous mutations in Rorb cause a gait phenotype, retinal abnormalities, and transcriptomic changes relevant to human neurodevelopmental conditions

“…In addition to the gait phenotype by which all mutants were identified, we also observed an absence of cone photoreceptors in Rorb h4/h4 and Rorb h5/h5 mutants. We also describe an expression pattern of Rorb in sensory areas, including the spinal cord, thalamus, and somatosensory cortex, consistent with previous studies (KOCH et al 2017;CLARK et al 2020). We have also demonstrated that, although the number of Rorb-expressing cells in somatosensory cortex is not dramatically different between mutant and WT mice, the expression of Scnn1a is markedly different, with many fewer cells labeled in mutant mice.…”

“…Further involvement of Rorb in the development of sensory systems of sensory signaling is evidenced by its embryonic requirement for proper formation of whisker barrels in the somatosensory cortex of mice (JABAUDON et al 2012) and its role in establishment of long-range axonal projections from the superior colliculus to the dorsal lateral geniculate nucleus and the pretectum (BYUN et al 2019). Disruption of cytoarchitectural patterning due to loss of Rorb may occur via a shift in cellular identity initiated through the downstream RORB target Thsd7a and/or changes in chromatin accessibility during development (CLARK et al 2020).…”

ROR: Nuclear Receptor for Melatonin or Not?

“…Moreover, various studies have reported that RORs mediate functions of melatonin [ 27 , 28 , 29 , 30 ] and that melatonin can regulate the transcriptional activity of RORs, boosting the transcription of ROR target genes [ 12 , 13 , 14 ]. However, RORs have also been found to function independently of melatonin-induced signalling [ 21 , 31 , 32 , 33 , 34 ].…”

“…Furthermore, RORβ plays a crucial role in perceptual and cognitive functions by facilitating the formation of layered structures in the cerebral cortex, which are derived from the migration and differentiation of neurons. RORβ reportedly acts as a marker for neurons in layers IV and V of the cerebral cortex, as well as in the barrel cortex [ 21 , 32 ]. Mutations in the human RORβ gene contribute to epilepsy and intellectual deficiencies [ 33 , 34 ].…”

Cell type resolved co-expression networks of core clock genes in brain development

“…Rorb, shows expression in the L4 region of the mouse and human brain (Zeng et al 2012). It also plays a vital role in the development and organization of the whisker barrel in rodent brain (Clark et al 2020). These studies provide hints for involvement of Hlf and Rorb in the brain development, additionally our analysis discloses their underlying gene regulatory network (Figure 2C & S1).…”