Kinesin Motor Domain Research Articles

Tether-scanning the kinesin motor domain reveals a core mechanical action

Natural kinesin motors are tethered to their cargoes via short C-terminal or N-terminal linkers, whose docking against the core motor domain generates directional force. It remains unclear whether linker docking is the only process contributing directional force or whether linker docking is coupled to and amplifies an underlying, more fundamental force-generating mechanical cycle of the kinesin motor domain. Here, we show that kinesin motor domains tethered via double-stranded DNAs (dsDNAs) attached to surface loops drive robust microtubule (MT) gliding. Tethering using dsDNA attached to surface loops disconnects the C-terminal neck-linker and the N-terminal cover strand so that their dock-undock cycle cannot exert force. The most effective attachment positions for the dsDNA tether are loop 2 or loop 10, which lie closest to the MT plus and minus ends, respectively. In three cases, we observed minus-end-directed motility. Our findings demonstrate an underlying, potentially ancient, force-generating core mechanical action of the kinesin motor domain, which drives, and is amplified by, linker docking.

Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy.

The study identifies novel genetic determinants of reproductive aging linked to egg aneuploidy by analyzing maternal exomes and demonstrates that variants in kinesin genes, specifically KIF18A , contribute to increased aneuploidy and accelerated reproductive aging, offering potential for personalized fertility medicine.

Dynamic localization of the chromosomal passenger complex in trypanosomes is controlled by the orphan kinesins KIN-A and KIN-B.

The chromosomal passenger complex (CPC) is an important regulator of cell division, which shows dynamic subcellular localization throughout mitosis, including kinetochores and the spindle midzone. In traditional model eukaryotes such as yeasts and humans, the CPC consists of the catalytic subunit Aurora B kinase, its activator INCENP, and the localization module proteins Borealin and Survivin. Intriguingly, Aurora B and INCENP as well as their localization pattern are conserved in kinetoplastids, an evolutionarily divergent group of eukaryotes that possess unique kinetochore proteins and lack homologs of Borealin or Survivin. It is not understood how the kinetoplastid CPC assembles nor how it is targeted to its subcellular destinations during the cell cycle. Here, we identify two orphan kinesins, KIN-A and KIN-B, as bona fide CPC proteins in Trypanosoma brucei, the kinetoplastid parasite that causes African sleeping sickness. KIN-A and KIN-B form a scaffold for the assembly of the remaining CPC subunits. We show that the C-terminal unstructured tail of KIN-A interacts with the KKT8 complex at kinetochores, while its N-terminal motor domain promotes CPC translocation to spindle microtubules. Thus, the KIN-A:KIN-B complex constitutes a unique 'two-in-one' CPC localization module, which directs the CPC to kinetochores from S phase until metaphase and to the central spindle in anaphase. Our findings highlight the evolutionary diversity of CPC proteins and raise the possibility that kinesins may have served as the original transport vehicles for Aurora kinases in early eukaryotes.

Abstract 5723: Selectivity profiling of small molecule kinesin inhibitors using microplate-based ATPase activity assay

Abstract Kinesin superfamily proteins (KIFs) are a large family of molecular motor proteins, that share a highly conserved motor domain. KIFs play an important role in cell division and transport of vesicles and organelles within cells. Mitotic kinesins hydrolyze ATP through its ATPase activity to move along the spindle microtubules and carry out several functions during mitosis to facilitate precise chromosome segregation. Altered expressions of several kinesins are shown in various cancers, fueling the aggressive nature of cancers leading to genomic instability. KIF11/Eg5 overexpression is shown in various cancers including hepatic carcinoma, lung, prostate, colorectal, gastric, and pancreatic cancers. Small molecule inhibitors of KIF11/Eg5 and CENP-E are shown to result in mitotic arrest leading to apoptosis in tumor cell lines. Despite the poor clinical outcome of several Eg5 and CENP-E inhibitors entered in clinical trials, targeting kinesins remains an attractive anti-cancer therapeutic approach. Recently, an inhibitor of KIF18A has entered clinical trial for treatment of solid tumors with high chromosomal instability. Here we show development of a microplate based biochemical screening assays for a panel of kinesin motor domain proteins. We summarize kinetic characterization of kinesin proteins and study the selectivity of various previously reported KIF18A, Eg5, CENP-E inhibitors across a kinesin selectivity panel. Citation Format: Brenna P. Lee, Sung Won Oh, Kurumi Y. Horiuchi, Safnas F. AbdulSalam. Selectivity profiling of small molecule kinesin inhibitors using microplate-based ATPase activity assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5723.

Dominant negative variants in KIF5B cause osteogenesis imperfecta via down regulation of mTOR signaling.

Kinesin motor proteins transport intracellular cargo, including mRNA, proteins, and organelles. Pathogenic variants in kinesin-related genes have been implicated in neurodevelopmental disorders and skeletal dysplasias. We identified de novo, heterozygous variants in KIF5B, encoding a kinesin-1 subunit, in four individuals with osteogenesis imperfecta. The variants cluster within the highly conserved kinesin motor domain and are predicted to interfere with nucleotide binding, although the mechanistic consequences on cell signaling and function are unknown. To understand the in vivo genetic mechanism of KIF5B variants, we modeled the p.Thr87Ile variant that was found in two patients in the C. elegans ortholog, unc-116, at the corresponding position (Thr90Ile) by CRISPR/Cas9 editing and performed functional analysis. Next, we studied the cellular and molecular consequences of the recurrent p.Thr87Ile variant by microscopy, RNA and protein analysis in NIH3T3 cells, primary human fibroblasts and bone biopsy. C. elegans heterozygous for the unc-116 Thr90Ile variant displayed abnormal body length and motility phenotypes that were suppressed by additional copies of the wild type allele, consistent with a dominant negative mechanism. Time-lapse imaging of GFP-tagged mitochondria showed defective mitochondria transport in unc-116 Thr90Ile neurons providing strong evidence for disrupted kinesin motor function. Microscopy studies in human cells showed dilated endoplasmic reticulum, multiple intracellular vacuoles, and abnormal distribution of the Golgi complex, supporting an intracellular trafficking defect. RNA sequencing, proteomic analysis, and bone immunohistochemistry demonstrated down regulation of the mTOR signaling pathway that was partially rescued with leucine supplementation in patient cells. We report dominant negative variants in the KIF5B kinesin motor domain in individuals with osteogenesis imperfecta. This study expands the spectrum of kinesin-related disorders and identifies dysregulated signaling targets for KIF5B in skeletal development.

Molecular Mapping of Biofortification Traits in Bread Wheat (Triticum aestivum L.) Using a High-Density SNP Based Linkage Map.

A set of 188 recombinant inbred lines (RILs) derived from a cross between a high-yielding Indian bread wheat cultivar HD2932 and a synthetic hexaploid wheat (SHW) Synthetic 46 derived from tetraploid Triticum turgidum (AA, BB 2n = 28) and diploid Triticum tauschii (DD, 2n = 14) was used to identify novel genomic regions associated in the expression of grain iron concentration (GFeC), grain zinc concentration (GZnC), grain protein content (GPC) and thousand kernel weight (TKW). The RIL population was genotyped using SNPs from 35K Axiom® Wheat Breeder's Array and 34 SSRs and phenotyped in two environments. A total of nine QTLs including five for GPC (QGpc.iari_1B, QGpc.iari_4A, QGpc.iari_4B, QGpc.iari_5D, and QGpc.iari_6B), two for GFeC (QGfec.iari_5B and QGfec.iari_6B), and one each for GZnC (QGznc.iari_7A) and TKW (QTkw.iari_4B) were identified. A total of two stable and co-localized QTLs (QGpc.iari_4B and QTkw.iari_4B) were identified on the 4B chromosome between the flanking region of Xgwm149-AX-94559916. In silico analysis revealed that the key putative candidate genes such as P-loop containing nucleoside triphosphatehydrolase, Nodulin-like protein, NAC domain, Purine permease, Zinc-binding ribosomal protein, Cytochrome P450, Protein phosphatase 2A, Zinc finger CCCH-type, and Kinesin motor domain were located within the identified QTL regions and these putative genes are involved in the regulation of iron homeostasis, zinc transportation, Fe, Zn, and protein remobilization to the developing grain, regulation of grain size and shape, and increased nitrogen use efficiency. The identified novel QTLs, particularly stable and co-localized QTLs are useful for subsequent use in marker-assisted selection (MAS).

Characterization of Microtubule Lattice Heterogeneity by Segmented Subtomogram Averaging.

Microtubule structure is commonly investigated using single-particle analysis (SPA) or subtomogram averaging (STA), whose main objectives are to gather high-resolution information on the αβ-tubulin heterodimer and on its interactions with neighboring molecules within the microtubule lattice. The maps derived from SPA approaches usually delineate a continuous organization of the αβ-tubulin heterodimer that alternate regularly head-to-tail along protofilaments, and that share homotypic lateral interactions between monomers (α-α, β-β), except at one unique region called the seam, made of heterotypic ones (α-β, β-α). However, this textbook description of the microtubule lattice has been challenged over the years by several studies that revealed the presence of multi-seams in microtubules assembled in vitro from purified tubulin. To analyze in deeper detail their intrinsic structural heterogeneity, we have developed a segmented subtomogram averaging (SSTA) strategy on microtubules decorated with kinesin motor-domains that bind every αβ-tubulin heterodimer. Individual protofilaments and microtubule centers are modeled, and sub-volumes are extracted at every kinesin motor domain position to obtain full subtomogram averages of the microtubules. The model is divided into shorter segments, and subtomogram averages of each segment are calculated using the main parameters of the full-length microtubule settings as a template. This approach reveals changes in the number and location of seams within individual microtubules assembled in vitro from purified tubulin and in Xenopus egg cytoplasmic extracts. Key features This protocol builds upon the method developed by J.M. Heumann to perform subtomogram averages of microtubules and extends it to divide them into shorter segments. Microtubules are decorated with kinesin motor-domains to determine the underlying organization of its constituent αβ-tubulin heterodimers. The SSTA approach allows analysis of the structural heterogeneity of individual microtubules and reveals multi-seams and changes in their number and location within their shaft. Graphical overview.

Electro-detachment of kinesin motor domain from microtubule in silico

Kinesin is a motor protein essential in cellular functions, such as intracellular transport and cell-division, as well as for enabling nanoscopic transport in bio-nanotechnology. Therefore, for effective control of function for nanotechnological applications, it is important to be able to modify the function of kinesin. To circumvent the limitations of chemical modifications, here we identify another potential approach for kinesin control: the use of electric forces. Using full-atom molecular dynamics simulations (247,358 atoms, total time ∼ 4.4 μs), we demonstrate, for the first time, that the kinesin-1 motor domain can be detached from a microtubule by an intense electric field within the nanosecond timescale. We show that this effect is field-direction dependent and field-strength dependent. A detailed analysis of the electric forces and the work carried out by electric field acting on the microtubule–kinesin system shows that it is the combined action of the electric field pulling on the β-tubulin C-terminus and the electric-field-induced torque on the kinesin dipole moment that causes kinesin detachment from the microtubule. It is shown, for the first time in a mechanistic manner, that an electric field can dramatically affect molecular interactions in a heterologous functional protein assembly. Our results contribute to understanding of electromagnetic field–biomatter interactions on a molecular level, with potential biomedical and bio-nanotechnological applications for harnessing control of protein nanomotors.

Motor generated torque drives coupled yawing and orbital rotations of kinesin coated gold nanorods

Kinesin motor domains generate impulses of force and movement that have both translational and rotational (torque) components. Here, we ask how the torque component influences function in cargo-attached teams of weakly processive kinesins. Using an assay in which kinesin-coated gold nanorods (kinesin-GNRs) translocate on suspended microtubules, we show that for both single-headed KIF1A and dimeric ZEN-4, the intensities of polarized light scattered by the kinesin-GNRs in two orthogonal directions periodically oscillate as the GNRs crawl towards microtubule plus ends, indicating that translocating kinesin-GNRs unidirectionally rotate about their short (yaw) axes whilst following an overall left-handed helical orbit around the microtubule axis. For orientations of the GNR that generate a signal, the period of this short axis rotation corresponds to two periods of the overall helical trajectory. Torque force thus drives both rolling and yawing of near-spherical cargoes carrying rigidly-attached weakly processive kinesins, with possible relevance to intracellular transport.

Magic-angle-spinning NMR structure of the kinesin-1 motor domain assembled with microtubules reveals the elusive neck linker orientation

Microtubules (MTs) and their associated proteins play essential roles in maintaining cell structure, organelle transport, cell motility, and cell division. Two motors, kinesin and cytoplasmic dynein link the MT network to transported cargos using ATP for force generation. Here, we report an all-atom NMR structure of nucleotide-free kinesin-1 motor domain (apo-KIF5B) in complex with paclitaxel-stabilized microtubules using magic-angle-spinning (MAS) NMR spectroscopy. The structure reveals the position and orientation of the functionally important neck linker and how ADP induces structural and dynamic changes that ensue in the neck linker. These results demonstrate that the neck linker is in the undocked conformation and oriented in the direction opposite to the KIF5B movement. Chemical shift perturbations and intensity changes indicate that a significant portion of ADP-KIF5B is in the neck linker docked state. This study also highlights the unique capability of MAS NMR to provide atomic-level information on dynamic regions of biological assemblies.

Synergistic autoinhibition and activation mechanisms control kinesin-1 motor activity.

SUMMARYKinesin-1 activity is regulated by autoinhibition. Intramolecular interactions within the kinesin heavy chain (KHC) are proposed to be one facet of motor regulation. The KHC also binds to the kinesin light chain (KLC), which has been implicated in both autoinhibition and activation of the motor. We show that the KLC inhibits the kinesin-microtubule interaction independently from the proposed intramolecular interaction within KHC. Cargo-adaptor proteins that bind the KLC stimulated processive movement, but the landing rate of activated kinesin complexes remained low. Microtubule-associated protein 7 (MAP7) enhanced motility by increasing the landing rate and run length of the activated kinesin motors. Our results support a model whereby the motor activity of the kinesin is regulated by synergistic inhibition mechanisms and that cargo-adaptor binding to the KLC releases both mechanisms. However, a non-motor MAP is required for robust microtubule association of the activated motor. Thus, human kinesin is regulated by synergistic autoinhibition and activation mechanisms.

Genetic and clinical analysis of KIF2A gene variant in a Chinese patient with complex cortical dysplasia and other brain malformations

To explore the genetic basis for a child featuring complex cortical dysplasia and other brain malformations (CDCBM3). Genomic DNA was extracted from peripheral blood samples from the patient and his parents. Whole exome sequencing (WES) was carried out for the family trio. Suspected variant was verified by Sanger sequencing. The proband, a 1-year-and-2-month old Chinese boy, had presented with motor developmental delay, lissencephaly, severe cognitive impairments, absent speech and congenital laryngomalacia. WES revealed that he has harbored a heterozygous missense variant of the KIF2A gene, namely NM_001098511.2: c.952G>A, p.Gly318Arg (GRCh37/hg19). The highly conserved residue is located around the ATP nucleotide-binding pocket in the kinesin motor domain (PM1). The variant was not found in the Genome Aggregation Database and the 1000 Genomes Project (PM2), and was predicted to be deleterious on the gene product by multiple in silico prediction tools (PP3). This variant was unreported previously and was de novo in origin (PS2). Based on the ACMG guidelines, it was categorized as likely pathogenic (PS2+PM1+PM2+PP3). Furthermore, the congenital laryngomalacia found in our patient was absent in previously reported CDCBM3 cases. The novel variant of the KIF2A gene probably underlay the disorders in the proband. Above finding has expanded the phenotypic and mutational spectrum of CDCBM3.

A neuropathy-associated kinesin KIF1A mutation hyper-stabilizes the motor-neck interaction during the ATPase cycle.

The mechanochemical coupling of ATPase hydrolysis and conformational dynamics in kinesin motors facilitates intramolecular interaction cycles between the kinesin motor and neck domains, which are essential for microtubule-based motility. Here, we characterized a charge-inverting KIF1A-E239K mutant that we identified in a family with axonal-type Charcot-Marie-Tooth disease and also in 24 cases in human neuropathies including spastic paraplegia and hereditary sensory and autonomic neuropathy. We show that Glu239 in the β7 strand is a key residue of the motor domain that regulates the motor-neck interaction. Expression of the KIF1A-E239K mutation has decreased ability to complement Kif1a+/- neurons, and significantly decreases ATPase activity and microtubule gliding velocity. X-ray crystallography shows that this mutation causes an excess positive charge on β7, which may electrostatically interact with a negative charge on the neck. Quantitative mass spectrometric analysis supports that the mutation hyper-stabilizes the motor-neck interaction at the late ATP hydrolysis stage. Thus, the negative charge of Glu239 dynamically regulates the kinesin motor-neck interaction, promoting release of the neck from the motor domain upon ATP hydrolysis.

Kinesin-binding protein remodels the kinesin motor to prevent microtubule binding.

Kinesins are regulated in space and time to ensure activation only in the presence of cargo. Kinesin-binding protein (KIFBP), which is mutated in Goldberg-Shprintzen syndrome, binds to and inhibits the catalytic motor heads of 8 of 45 kinesin superfamily members, but the mechanism remains poorly defined. Here, we used cryo–electron microscopy and cross-linking mass spectrometry to determine high-resolution structures of KIFBP alone and in complex with two mitotic kinesins, revealing structural remodeling of kinesin by KIFBP. We find that KIFBP remodels kinesin motors and blocks microtubule binding (i) via allosteric changes to kinesin and (ii) by sterically blocking access to the microtubule. We identified two regions of KIFBP necessary for kinesin binding and cellular regulation during mitosis. Together, this work further elucidates the molecular mechanism of KIFBP-mediated kinesin inhibition and supports a model in which structural rearrangement of kinesin motor domains by KIFBP abrogates motor protein activity.

Molecular chaperone Hsp90 protects KCBP from degradation by proteasome in Dunaliella salina cells.

Kinesin-like calmodulin-binding protein (KCBP) is a unique kinesin with half kinesin and half myosin, with kinesin motor domain at C-terminus and myosin tail homology region 4 (MyTH4) and band 4.1, ezrin, radixin, moesin (FERM) domains at N-terminus. The special structure endows KCBP multi-intracellular functions, including cell division, trichome morphogenesis in plants, and flagellar function in algae. However, little is known about the molecular mechanism underlying these functions. Here, we identified a molecular chaperone Hsp90 as a novel binding partner with KCBP in Dunaliella salina using a yeast two-hybrid screen. Further analysis showed that Hsp90 interacted with both the N-terminal and C-terminal of DsKCBP. Since Hsp90 was involved in the stability and proteolytic turnover of numerous proteins, whether Hsp90 regulated the degradation of DsKCBP was investigated. Our results showed that both Hsp90 and DsKCBP presented in the purified proteasome, and the interaction of DsKCBP-Hsp90 was inhibited upon Hsp90 inhibitor geldanamycin treatment. The level of DsKCBP proteins was diminished remarkably indicating that the disassociation of DsKCBP from Hsp90 accelerated the degradation of the former. Furthermore, immunofluorescence results showed that the localization of DsKCBP at basal body and flagella was disappeared by Hsp90 inhibition. The increased mRNA level of DsKCBP during flagellar assembly was not obvious by geldanamycin treatment. These data provided evidence that Hsp90 protected DsKCBP from degradation by proteasome and was involved in the role of DsKCBP in flagellar assembly.

The kinesin of the flagellum attachment zone in Leishmania is required for cell morphogenesis, cell division and virulence in the mammalian host

Leishmania parasites possess a unique and complex cytoskeletal structure termed flagellum attachment zone (FAZ) connecting the base of the flagellum to one side of the flagellar pocket (FP), an invagination of the cell body membrane and the sole site for endocytosis and exocytosis. This structure is involved in FP architecture and cell morphogenesis, but its precise role and molecular composition remain enigmatic. Here, we characterized Leishmania FAZ7, the only known FAZ protein containing a kinesin motor domain, and part of a clade of trypanosomatid-specific kinesins with unknown functions. The two paralogs of FAZ7, FAZ7A and FAZ7B, display different localizations and functions. FAZ7A localizes at the basal body, while FAZ7B localizes at the distal part of the FP, where the FAZ structure is present in Leishmania. While null mutants of FAZ7A displayed normal growth rates, the deletion of FAZ7B impaired cell growth in both promastigotes and amastigotes of Leishmania. The kinesin activity is crucial for its function. Deletion of FAZ7B resulted in altered cell division, cell morphogenesis (including flagellum length), and FP structure and function. Furthermore, knocking out FAZ7B induced a mis-localization of two of the FAZ proteins, and disrupted the molecular organization of the FP collar, affecting the localization of its components. Loss of the kinesin FAZ7B has important consequences in the insect vector and mammalian host by reducing proliferation in the sand fly and pathogenicity in mice. Our findings reveal the pivotal role of the only FAZ kinesin as part of the factors important for a successful life cycle of Leishmania.

A highly conserved 310 helix within the kinesin motor domain is critical for kinesin function and human health.

KIF1A is a critical cargo transport motor within neurons. More than 100 known mutations result in KIF1A-associated neurological disorder (KAND), a degenerative condition for which there is no cure. A missense mutation, P305L, was identified in children diagnosed with KAND, but the molecular basis for the disease is unknown. We find that this conserved residue is part of an unusual 310 helix immediately adjacent to the family-specific K-loop, which facilitates a high microtubule-association rate. We find that the mutation negatively affects several biophysical parameters of the motor. However, the microtubule-association rate of the motor is most markedly affected, revealing that the presence of an intact K-loop is not sufficient for its function. We hypothesize that the 310 helix facilitates a specific K-loop conformation that is critical for its function. We find that the function of this proline is conserved in kinesin-1, revealing a fundamental principle of the kinesin motor mechanism.

Cryo-EM of kinesin-binding protein: challenges and opportunities from protein-surface interactions.

Kinesin-binding protein (KBP) is an important selective inhibitor of specific kinesin family members and its genetic disruption causes Goldberg-Shprintzen syndrome. Cryo-electron microscopy (cryo-EM) has recently been used to reveal the structure of KBP alone (72 kDa) and in complex with the motor domain of the mitotic kinesin-12 KIF15 (110 kDa). KBP is an α-solenoid, tetratricopeptide-repeat protein that interacts with the microtubule-binding region of the kinesin motor domain and blocks microtubule attachment. Numerous challenges arose relating to the behavior of KBP and KBP-kinesin complexes during cryo-EM sample preparation. These included the partial denaturation of KBP by air-water interfaces, protein aggregation resulting from carbon interaction and preferential orientation. Sample preparation with a graphene oxide substrate enabled the eventual structure determination. Here, experiences with preparing these samples are detailed, bringing attention to some of the challenges and opportunities that are likely to arise from protein-surface interactions.

The Mechanism of Selective Kinesin Inhibition by Kinesin Binding Protein

Spatial and temporal regulation of kinesin activity is essential for a diversity of eukaryotic cellular processes including mitosis and intracellular cargo distribution. Kinesin binding protein (KBP), derived from the causal gene in Goldberg-Shprintzen syndrome, binds a select subset of kinesin motor domains and inhibits their microtubule attachment, however the structural mechanisms behind this activity have been unclear. Here we use cryo-electron microscopy to reveal the structure of KBP and of a KBP-kinesin motor domain complex.

Variants in KIF2A cause broad clinical presentation; the computational structural analysis of a novel variant in a patient with a cortical dysplasia, complex, with other brain malformations 3

Cortical dysplasia, complex, with other brain malformations 3 (CDCBM3) is a rare autosomal dominant syndrome caused by Kinesin family Member 2A (KIF2A) gene mutation. Patients with CDCBM3 exhibit posterior dominant agyria/pachygyria with severe motor dysfunction. Here, we report an 8-year-old boy with CDCBM3 showing a typical, but relatively mild, clinical presentation of CDCBM3 features. Whole-exome sequencing identified a heterozygous mutation of NM_001098511.2:c.1298C>A [p.(Ser433Tyr)]. To our knowledge, the mutation has never been reported previously. The variant was located distal to the nucleotide binding domain (NBD), in which previously-reported variants in CDCBM3 patients have been located. The computational structural analysis showed the p.433 forms the pocket with NBD. Variants in KIF2A have been reported in the NBD for CDCBM3, in the kinesin motor 3 domain, but not in the NBD in epilepsy, and outside of the kinesin motor domain in autism spectrum syndrome, respectively. Our patient has a variant, that is not in the NBD but at the pocket with the NBD, resulting in a clinical features of CDCBM3 with mild symptoms. The clinical findings of patients with KIF2A variants appear restricted to the central nervous system and facial anomalies. We can call this spectrum "KIF2A syndrome" with variable severity.