DYNC1H1 mutation alters transport kinetics and ERK1/2-cFos signalling in a mouse model of distal spinal muscular atrophy

Abstract

Mutations in the gene encoding the heavy chain subunit (DYNC1H1) of cytoplasmic dynein cause spinal muscular atrophy with lower extremity predominance, Charcot-Marie-Tooth disease and intellectual disability. We used the legs at odd angles (Loa) (DYNC1H1(F580Y)) mouse model for spinal muscular atrophy with lower extremity predominance and a combination of live-cell imaging and biochemical assays to show that the velocity of dynein-dependent microtubule minus-end (towards the nucleus) movement of EGF and BDNF induced signalling endosomes is significantly reduced in Loa embryonic fibroblasts and motor neurons. At the same time, the number of the plus-end (towards the cell periphery) moving endosomes is increased in the mutant cells. As a result, the extracellular signal-regulated kinases (ERK) 1/2 activation and c-Fos expression are altered in both mutant cell types, but the motor neurons exhibit a strikingly abnormal ERK1/2 and c-Fos response to serum-starvation induced stress. These data highlight the cell-type specific ERK1/2 response as a possible contributory factor in the neuropathological nature of Dync1h1 mutations, despite generic aberrant kinetics in both cell types, providing an explanation for how mutations in the ubiquitously expressed DYNC1H1 cause neuron-specific disease.

DYNC1H1 mutations associated with neurological diseases compromise processivity of dynein–dynactin–cargo adaptor complexes

“…This observation, together with the failure to detect nonsense, frameshift, or deletion alleles of DYNC1H1 in humans with SMALED or MCD, indicates that disease-associated mutations have a dominant-negative or dominant gain-of-function effect. However, with the exception of the mouse Legs at odd angles (Loa) mutation (20)(21)(22)(23)(24), the effects of human and mouse mutations on the motility of the dynein complex have not been investigated in detail.…”

A mathematical understanding of how cytoplasmic dynein walks on microtubules

“…It must be noted, however, that this reflects the position of the tail of dynein rather than the motor domain, and further investigations have shown that the motors move with a usual step size of around 16 nm [36,37,48]. Moreover, we note that dynein steps are not always parallel to the microtubule and usually have off-axis components [10,36,37,48], and dynein can also take backward steps [47,48]. Carter et al [50] proposed that the stalk acts as a tether in the stepping process and that the MTBD determines the direction of the step, while Redwine et al [51] proposed that conformational changes in the MTBD lead to movement in the linker domain and hence displacement of the MTBD.…”

“…Errors in the heavy chain of dynein, encoded by dynein cytoplasmic 1 heavy chain 1 ( DYNC1H1 ) gene, have been implicated in spinal muscular atrophy with lower extremity predominance (SMA-LED), Charcot-Marie-Tooth disease type 2 (CMT2) and intellectual disability (reviewed in [8]; see also [9]). Investigations into mutations in dynein have shown particular behavioural differences, such as a decrease in velocity and distance travelled in a mouse strain known as ‘Legs at odd angles’ ( Loa ) [10–12]. Studies by Hafezparast et al [10,13], have shown that the DYNC1H1 F 580 Y mutation in the Loa mouse strain negatively affects fast retrograde transport mediated by dynein, including an increase in pauses in motion.…”

“…Investigations into mutations in dynein have shown particular behavioural differences, such as a decrease in velocity and distance travelled in a mouse strain known as ‘Legs at odd angles’ ( Loa ) [10–12]. Studies by Hafezparast et al [10,13], have shown that the DYNC1H1 F 580 Y mutation in the Loa mouse strain negatively affects fast retrograde transport mediated by dynein, including an increase in pauses in motion. Work by Deng et al [14], has shown that the Loa mutation gives rise to a lower affinity of dynein to dynactin, which regulates cargo binding and dynein processivity.…”

“…Work by Deng et al [14], has shown that the Loa mutation gives rise to a lower affinity of dynein to dynactin, which regulates cargo binding and dynein processivity. The devastating effect of dynein malfunction presented in mutation studies on mouse models as well as in humans shows the need for greater understanding of the mechanics and processes used by dynein [8–10,13]. The dynein family is particularly interesting as it has evolved separately from other motor protein families, kinesin and myosin, and has a very different structure and mechanics (see [15] for a detailed review).…”