Trisomy 21 induces pericentrosomal crowding delaying primary ciliogenesis and mouse cerebellar development

Abstract

Trisomy 21, the genetic cause of Down syndrome, disrupts primary cilia formation and function, in part through elevated Pericentrin, a centrosome protein encoded on chromosome 21. Yet how trisomy 21 and elevated Pericentrin disrupt cilia-related molecules and pathways, and the in vivo phenotypic relevance remain unclear. Utilizing ciliogenesis time course experiments combined with light microscopy and electron tomography, we reveal that chromosome 21 polyploidy elevates Pericentrin and microtubules away from the centrosome that corral MyosinVA and EHD1, delaying ciliary membrane delivery and mother centriole uncapping essential for ciliogenesis. If given enough time, trisomy 21 cells eventually ciliate, but these ciliated cells demonstrate persistent trafficking defects that reduce transition zone protein localization and decrease sonic hedgehog signaling in direct anticorrelation with Pericentrin levels. Consistent with cultured trisomy 21 cells, a mouse model of Down syndrome with elevated Pericentrin has fewer primary cilia in cerebellar granule neuron progenitors and thinner external granular layers at P4. Our work reveals that elevated Pericentrin from trisomy 21 disrupts multiple early steps of ciliogenesis and creates persistent trafficking defects in ciliated cells. This pericentrosomal crowding mechanism results in signaling deficiencies consistent with the neurological phenotypes found in individuals with Down syndrome.

Key role of vimentin in the organization of the primary cilium

“…Our observations are consistent with a recent report indicating that vimentin "mediates" the structure of the pericentriolar material and its absence correlates with a decrease of pericentrin at the centrosome [50]. On the other hand, elevated pericentrin, as observed in trisomy 21 delays primary ciliogenesis by disrupting multiple early steps of this process, and decreases sonic hedgehog signaling [40]. This indicates that pericentrin levels and distribution need to be tightly controlled for correct cilia formation.…”

“…In view of the abnormal distribution of both acetylated tubulin and γ-tubulin observed in MEF Vim(-/-) , we explored the distribution of pericentrin, a protein critical for the formation of primary cilia, which controls the traffic of intracellular material around the centrosome [40], and contributes to nucleate the microtubules by interacting with γ-tubulin [41]. Pericentrin is normally located around the centrioles at the base of primary cilia and its depletion impairs ciliogenesis [41].…”

Circadian oscillation in primary cilium length by clock genes regulates fibroblast cell migration

“…PCNT forms a complex with intraflagellar transport (IFT) proteins and polycystin‐2 (PC2), which is reportedly required for the assembly of primary cilia (Jurczyk et al , 2004). In contrast, in trisomy 21, the most prevalent human chromosomal disorder, an excessive increase in PCNT inhibits the transport of centrosome and cilia proteins, resulting in defects in cilia formation (Galati et al , 2018; McCurdy et al , 2022; Jewett et al , 2023). In this study, PCNT‐positive centriolar satellites transiently increased in NIH/3T3 cells 30 h after synchronization when the primary cilium length was minimal.…”

Circadian oscillation in primary cilium length by clock genes regulate fibroblast cell migration

“…PCNT forms a complex with intraflagellar transport (IFT) proteins and polycystin-2 (PC2), which is reportedly required for the assembly of primary cilia (Jurczyk et al ., 2004). In contrast, in trisomy 21, the most prevalent human chromosomal disorder, an excessive increase in PCNT inhibits the transport of centrosome and cilia proteins, resulting in defects in cilia formation (Galati et al , 2018; Jewett et al , 2023; McCurdy et al , 2022). In this study, PCNT-positive centriolar satellites transiently increased in NIH/3T3 cells 30 h after synchronization when the primary cilium length was minimal.…”