A High-Throughput Platform to Identify Small-Molecule Inhibitors of CRISPR-Cas9.

The precise control of CRISPR-Cas9 activity is required for a number of genome engineering technologies. Here, we report a generalizable platform that provided the first synthetic small-molecule inhibitors of Streptococcus pyogenes Cas9 (SpCas9) that weigh <500 Da and are cell permeable, reversible, and stable under physiological conditions. We developed a suite of high-throughput assays for SpCas9 functions, including a primary screening assay for SpCas9 binding to the protospacer adjacent motif, and used these assays to screen a structurally diverse collection of natural-product-like small molecules to ultimately identify compounds that disrupt the SpCas9-DNA interaction. Using these synthetic anti-CRISPR small molecules, we demonstrated dose and temporal control of SpCas9 and catalytically impaired SpCas9 technologies, including transcription activation, and identified a pharmacophore for SpCas9 inhibition using structure-activity relationships. These studies establish a platform for rapidly identifying synthetic, miniature, cell-permeable, and reversible inhibitors against both SpCas9 and next-generation CRISPR-associated nucleases.

Expansion of tumor-infiltrating lymphocytes in non-small cell lung cancer: Clinical potential and efficacy in EGFR mutation subsets.

Our study aimed to expand tumor-infiltrating lymphocytes (TILs) from primary non-small cell lung cancers (NSCLCs) and evaluate their reactivity against tumor cells. We expanded TILs from 103 primary NSCLCs using histopathological analysis, flow cytometry, IFN-γ release assays, cell-mediated cytotoxicity assays, and in vivo efficacy tests. TIL expansion was observed in all cases, regardless of EGFR mutation status. There was also an increase in the median CD4+/CD8+ ratio during expansion. In post-rapid expansion protocol (REP) TILs, 13 out of 16 cases, including all three cases with EGFR mutations, exhibited a two-fold or greater increase in IFN-γ secretion. The cytotoxicity assay revealed enhanced tumor cell death in three of the seven cases, two of which had EGFR mutations. In vivo functional testing in a patient-derived xenograft model showed a reduction in tumor volume. The anti-tumor activity of post-REP TILs underscores their potential as a therapeutic option for advanced NSCLC, irrespective of mutation status.

SARS-CoV-2 spike trimer vaccine expressed in Nicotiana benthamiana adjuvanted with Alum elicits protective immune responses in mice.

The ongoing coronavirus disease 2019 (COVID-19) pandemic has spurred rapid development of vaccines as part of the public health response. However, the general strategy used to construct recombinant trimeric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) proteins in mammalian cells is not completely adaptive to molecular farming. Therefore, we generated several constructs of recombinant S proteins for high expression in Nicotiana benthamiana. Intramuscular injection of N. benthamiana-expressed Sct vaccine (NSct Vac) into Balb/c mice elicited both humoral and cellular immune responses, and booster doses increased neutralizing antibody titres. In human angiotensin-converting enzyme knock-in mice, two doses of NSct Vac induced anti-S and neutralizing antibodies, which cross-neutralized Alpha, Beta, Delta and Omicron variants. Survival rates after lethal challenge with SARS-CoV-2 were up to 80%, without significant body weight loss, and viral titres in lung tissue fell rapidly, with no infectious virus detectable at 7-day post-infection. Thus, plant-derived NSct Vac could be a candidate COVID-19 vaccine.

Phenotypic Differences of CD103+ Tissue-Resident Memory T Cells Associated with Various Cancers.

BACKGROUND/AIMS: The presence and clinical importance of tissue-resident memory T (TRM) cells have been recently described in association with various cancer types. However, the frequency and the traditional naïve-effector-memory phenotypic characteristics of TRM cells are largely unknown. METHODS: We analyzed single-cell populations of colorectal cancer (CC, n = 18), stomach cancer (SC, n = 13), renal cell carcinoma (RCC, n = 19), and breast cancer (BC, n = 16) by dissociation of tumor tissue with collagenase/hyaluronidase. We investigated populations of naïve, effector, and memory T and TRM cells by flow cytometry. RESULTS: Among CD8- cells, CC was associated with a significantly higher proportion of CD103+ T cells than other tumor types (p < 0.001). Among CD8+ cells, CC and SC were associated with higher CD103+ T-cell proportions than RCC and BC (p < 0.001). Significantly more CD8+ than CD8- cells expressed CD103 (p < 0.001). In association with SC, RCC, and BC, CD8+ T cells had a similar T-cell phenotype composition pattern: fewer effector T cells and more memory-type T cells among CD103+ cells compared with CD103- cells (p < 0.05). Tumors with higher proportion of CD103+ cells had no specific clinicopathologic characteristics than those with lower proportion of CD103+ cells. CONCLUSION: TRM cell abundance and phenotypes varied among CC, SC, RCC, and BC. Further studies regarding the functional differences of TRM associated with various tumors are warranted.

The effects of a mobile application for patient participation to improve patient safety.

BACKGROUND: Patient participation in patient safety activities in care processes is a fundamental element of safer care. Patients play an important role in preventing patient safety incidents and improving health outcomes. Therefore, healthcare providers need to develop and provide educational materials and actionable tools for patient participation. OBJECTIVES: This study aimed to develop a mobile application for health consumers' participation and evaluate the effect of the mobile application on improving health consumers' participation in patient safety. METHODS: A quasi-experimental design was adopted. We developed a mobile application on the basis of a needs assessment, literature review, compilation of patient safety topics, and validity testing of the application. The target population included Korean adults aged between 30 and 65 years who had visited a medical institution more than once within the most recent 6 months. The intervention group received patient participation training by using the mobile application, Application for Patient Participation in Safety Enhancement, for 2 months. The primary outcome variables were patient safety knowledge, self-efficacy of participation, willingness to participate and experience of patient participation in patient safety activities. End-user satisfaction was assessed using a questionnaire. To assess participants' experiences with the intervention, qualitative data were collected through a focus group interview and open-ended responses to an end-user satisfaction survey. RESULTS: The intervention group (n = 60) had significantly higher overall average scores than the control group (n = 37) with regard to patient safety knowledge (p < .001), self-efficacy of participation (p = .001), willingness to participate (p = .010) and experience of participation (p = .038) in the post-survey. The total mean end-user satisfaction score was 3.56 ± 0.60. The participants expressed the realization that patients could play an important role in improving patient safety. CONCLUSIONS: This study demonstrated that educating health consumers through a mobile application with useful information improves patient participation in patient safety activities. Educational materials and patient participation tools could motivate health consumers' health-related behaviours. PATIENT OR PUBLIC CONTRIBUTION: Patients were involved during the programme development and evaluation.

Pleuropulmonary Blastoma with Hotspot Mutations in RNase IIIb Domain of DICER 1: Clinicopathologic Study of 10 Cases in a Single-Institute Experience.

INTRODUCTION: Pleuropulmonary blastoma (PPB) is a rare sarcomatous malignancy involving the lung and pleura which occurs in early childhood. Cystic PPB in the early stage can be misdiagnosed as other cystic diseases. Early detection of this entity is important for appropriate treatment and prevention of disease progression. Hotspot mutations in the ribonuclease IIIb (RNase IIIb) domain of DICER1 have been reported to have a crucial role as genetic factors of PPB and DICER1 familial syndrome. We reviewed the clinicopathologic findings of PPB and the status of DICER1 hotspot mutation and patients' clinical course. METHODS: We retrospectively reviewed all patients with histologically confirmed PPB at Asan Medical Center between 2000 and 2017. Ten cases were identified in the database, and their clinicopathologic parameters were evaluated. PPB was classified into the following 3 pathologic subtypes: type I (purely cystic), type II (mixed cystic and solid), and type III (entirely solid). The status of DICER1 mutation in 2 hotspot regions of the RNase IIIb domain was evaluated by Sanger sequencing. RESULTS: The most frequent PPB type was II (6 cases), followed by I and III (2 cases each). The age at diagnosis ranged from 16 months to 15 years. All patients underwent surgery, and all patients received adjuvant or neoadjuvant chemotherapy. Four of 7 patients had missense mutations in the RNase IIIb hotspot; the base and predicted corresponding amino acid changes were c.5113 G>A (p.E1705K), c.5407 G>A (p.E1803K), c.5425 G>A (p.G1809R), and c.5428 G>T (p.D1810Y). There was no particular association between the presence of the hotspot mutation and histologic type. Nine patients survived with no evidence of disease for a median interval of 93 (range, 13-199) months. Only 1 patient diagnosed with type III PPB at the age of 18 years had recurrence after 20.8 months and eventually died 66 months after the initial diagnosis. CONCLUSIONS: Late detection of solid PPB is associated with poor prognosis. Considering the rarity of PPB disease and the importance of DICER1 hotspot mutation in pathogenesis, DICER1 hotspot mutation testing and identification in the early cystic stage can improve patient outcomes.

Native Zinc Catalyzes Selective and Traceless Release of Small Molecules in ß-Cells.

The loss of insulin-producing ß-cells is the central pathological event in type 1 and 2 diabetes, which has led to efforts to identify molecules to promote ß-cell proliferation, protection, and imaging. However, the lack of ß-cell specificity of these molecules jeopardizes their therapeutic potential. A general platform for selective release of small-molecule cargoes in ß-cells over other islet cells ex vivo or other cell-types in an organismal context will be immensely valuable in advancing diabetes research and therapeutic development. Here, we leverage the unusually high Zn(II) concentration in ß-cells to develop a Zn(II)-based prodrug system to selectively and tracelessly deliver bioactive small molecules and fluorophores to ß-cells. The Zn(II)-targeting mechanism enriches the inactive cargo in ß-cells as compared to other pancreatic cells; importantly, Zn(II)-mediated hydrolysis triggers cargo activation. This prodrug system, with modular components that allow for fine-tuning selectivity, should enable the safer and more effective targeting of ß-cells.

Presence of tertiary lymphoid structures determines the level of tumor-infiltrating lymphocytes in primary breast cancer and metastasis.

The level of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures are significant prognostic and predictive factors in primary breast cancer. However, the understanding about differences in tumor-infiltrating lymphocytes and tertiary lymphoid structures at various metastatic sites or between primary breast tumors and metastatic sites is limited. A total of 335 cases of metastatic breast cancer from four metastatic sites (lung, liver, brain, and ovary) were included. We analyzed the percentages of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures in the primary and metastatic sites. The mean level of tumor-infiltrating lymphocytes in the lung metastases was higher than in the liver, brain, ovary, and matched primary tumors, while metastatic tumors of the liver and brain showed lower levels of tumor-infiltrating lymphocytes than primary tumors. Tertiary lymphoid structures were only found in the lung and liver, and in cases of brain metastases the change of tertiary lymphoid structures from present to absent significantly affected the level of tumor-infiltrating lymphocytes in metastases compared with that in matched primary tumors. Patients with a lower histological grade, hormone receptor positivity in primary tumors and metastases, a lower level of tumor-infiltrating lymphocytes and absence of tertiary lymphoid structures in primary tumors, a higher level of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures in metastases, and lung metastases showed significantly better overall survival. Our results showed that metastatic breast tumors in the lung had more tumor-infiltrating lymphocytes than did tumors at other sites and matched primary tumors. In addition, the presence of tertiary lymphoid structures in metastatic sites is a critical factor for the level of tumor-infiltrating lymphocytes.

Structure Determination of a Chloroenyne from Laurencia majuscula Using Computational Methods and Total Synthesis.

Despite numerous advances in spectroscopic methods through the latter part of the 20th century, the unequivocal structure determination of natural products can remain challenging, and inevitably, incorrect structures appear in the literature. Computational methods that allow the accurate prediction of NMR chemical shifts have emerged as a powerful addition to the toolbox of methods available for the structure determination of small organic molecules. Herein, we report the structure determination of a small, stereochemically rich natural product from Laurencia majuscula using the powerful combination of computational methods and total synthesis, along with the structure confirmation of notoryne, using the same approach. Additionally, we synthesized three further diastereomers of the L. majuscula enyne and have demonstrated that computations are able to distinguish each of the four synthetic diastereomers from the 32 possible diastereomers of the natural product. Key to the success of this work is to analyze the computational data to provide the greatest distinction between each diastereomer, by identifying chemical shifts that are most sensitive to changes in relative stereochemistry. The success of the computational methods in the structure determination of stereochemically rich, flexible organic molecules will allow all involved in structure determination to use these methods with confidence.

Development and comparison of two H5N8 influenza A vaccine candidate strains.

Avian influenza viruses circulating in birds have caused outbreaks of infection in poultry and humans, thereby threatening public health. Recently, a highly pathogenic avian influenza (HPAI) virus (H5N8) of clade 2.3.4.4 emerged in Korea and other countries and caused multiple outbreaks in domestic and wild birds, with concerns for human infection. To combat HPAI viral infections, novel vaccines are likely to be the most effective approach. Therefore, in this study, we generated H5N8 vaccine candidate viruses based on a Korean isolate (A/broiler duck/Korea/Buan2/2014). The vaccine candidate viruses were 2:6 reassortants expressing the two surface glycoproteins of A/broiler duck/Korea/Buan2/2014 on an A/Puerto Rico/8/34 (PR8) backbone generated by using an eight-plasmid-based reverse genetics system with or without replacement of the multi-basic amino acid cleavage motif (MBCM, a crucial pathogenic factor in HPAI virus) with a bi-basic amino acid cleavage motif (BBCM) in their HA. An H5N8 vaccine candidate virus containing the BBCM showed attenuated pathogenesis in embryonated eggs and exhibited less virulence in the infected mice compared with the wild H5N8 virus containing an MBCM. Vaccination with an inactivated preparation of the vaccine candidate virus protected mice from lethal H5N8 viral challenge. This is the first report of the development and evaluation of H5N8 vaccine strains (with an MBCM or BBCM) of HA clade 2.3.4.4 as vaccine candidates. Our findings suggest that H5N8 strains with a BBCM instead of an MBCM might be considered for H5N8 vaccine seed virus development or as a reference vaccine against H5N8 viral strains.

Mycophenolic mofetil, an alternative antiviral and immunomodulator for the highly pathogenic avian influenza H5N1 virus infection.

Infection with the highly pathogenic avian influenza H5N1 virus results in a high incidence of mortality in humans. Severe complications from infection are often associated with hypercytokinemia. However, current neuraminidase inhibitors (NAIs) have several limitations including the appearance of oseltamivir-resistant H5N1 virus and the inability to completely ameliorate hyper-immune responses. To overcome these limitations, we evaluated the anti-viral activity of mycophenolic mofetil (MMF) against A/Vietnam/1194/2004 (H5N1) virus infection using MDCK cells and mice. The IC50 of MMF (0.94 µM) was comparable to that of zanamivir (0.87 µM) in H5N1 virus-infected MDCK cells based on ELISA. Time-course assays demonstrated that MMF completely inhibited H5N1 viral mRNA replication and protein expression for approximately 8 h after the initiation of treatment. In addition, MMF treatment protected 100% of mice, and lung viral titers were substantially reduced. The anti-viral mechanism of MMF against H5N1 virus infection was further confirmed to depend on the inhibition of cellular inosine monophosphate dehydrogenase (IMPDH) by exogenous guanosine, which inhibits viral mRNA and protein expression. Moreover, IL-1ß, IFN-ß, IL-6, and IP-10 mRNA expression levels were significantly downregulated in MDCK cells with MMF treatment. These results indicated that MMF could represent a novel inhibitor of viral replication and a potent immunomodulator for the treatment of H5N1 virus infection.

ADAR1 expression is associated with tumour-infiltrating lymphocytes in triple-negative breast cancer.

Tumours with a high mutation burden exhibit considerable neoantigens and tumour-infiltrating lymphocytes. RNA editing by ADAR1 is a source of changes in epitope. However, ADAR1 expression in cancer cells and tumour-infiltrating lymphocyte levels in triple-negative breast cancer have not been well evaluated. We immunohistochemically examined ADAR1 expression in 681 triple-negative breast cancer patients and analysed their clinicopathological characteristics. We also analysed basal-like tumours using The Cancer Genome Atlas data. Among the 681 triple-negative breast cancer patients, 45.8% demonstrated high ADAR1 expression. Tumours with high ADAR1 expression exhibited high tumour-infiltrating lymphocyte levels, considerable CD8 + T lymphocyte infiltration, high histological grade and high expression of interferon-related proteins, including HLA-ABC, MxA and PKR. Among patients with lymph node metastasis, those with high tumour-infiltrating lymphocyte levels and low ADAR1 expression demonstrated the best disease-free survival. The Cancer Genome Atlas data analysis of basal-like tumours revealed significant positive correlation between ADAR1 and CD8B expression and positive association of high ADAR1 expression with immune responses and apoptosis pathways. We detected high ADAR1 expression in half of the triple-negative breast cancer patients. In addition to DNA mutations, RNA editing can be related to neoantigens; hence, we need to explore non-synonymous mutations exclusively found using RNA sequencing data to identify clinically relevant neoantigens.

Multisite phosphorylation of C-Nap1 releases it from Cep135 to trigger centrosome disjunction.

During mitotic entry, centrosomes separate to establish the bipolar spindle. Delays in centrosome separation can perturb chromosome segregation and promote genetic instability. However, interphase centrosomes are physically tethered by a proteinaceous linker composed of C-Nap1 (also known as CEP250) and the filamentous protein rootletin. Linker disassembly occurs at the onset of mitosis in a process known as centrosome disjunction and is triggered by the Nek2-dependent phosphorylation of C-Nap1. However, the mechanistic consequences of C-Nap1 phosphorylation are unknown. Here, we demonstrate that Nek2 phosphorylates multiple residues within the C-terminal domain of C-Nap1 and, collectively, these phosphorylation events lead to loss of oligomerization and centrosome association. Mutations in non-phosphorylatable residues that make the domain more acidic are sufficient to release C-Nap1 from the centrosome, suggesting that it is an increase in overall negative charge that is required for this process. Importantly, phosphorylation of C-Nap1 also perturbs interaction with the core centriolar protein, Cep135, and interaction of endogenous C-Nap1 and Cep135 proteins is specifically lost in mitosis. We therefore propose that multisite phosphorylation of C-Nap1 by Nek2 perturbs both oligomerization and Cep135 interaction, and this precipitates centrosome disjunction at the onset of mitosis.

Asymmetric spindle pole formation in CPAP-depleted mitotic cells.

CPAP is an essential component for centriole formation. Here, we report that CPAP is also critical for symmetric spindle pole formation during mitosis. We observed that pericentriolar material between the mitotic spindle poles were asymmetrically distributed in CPAP-depleted cells even with intact numbers of centrioles. The length of procentrioles was slightly reduced by CPAP depletion, but the length of mother centrioles was not affected. Surprisingly, the young mother centrioles of the CPAP-depleted cells are not fully matured, as evidenced by the absence of distal and subdistal appendage proteins. We propose that the selective absence of centriolar appendages at the young mother centrioles may be responsible for asymmetric spindle pole formation in CPAP-depleted cells. Our results suggest that the neural stem cells with CPAP mutations might form asymmetric spindle poles, which results in premature initiation of differentiation.

The causal relationship of serum uric acid on colorectal cancer: A Mendelian randomization study.

Colorectal cancer (CRC) is a significant public health issue owing to its widespread occurrence and substantial morbidity and mortality rates. Recent studies have highlighted serum uric acid (SUA) level as a probable risk factor for CRC; however, the inconsistency in these findings has created doubt. We performed a Mendelian randomization (MR) study utilizing extensive cohort data from the UK BioBank and the NHGRI-EBI Genome-Wide Association Study (GWAS) Catalog to investigate the causal connection between SUA levels and CRC incidence. Our MR study addresses the constraints of earlier studies, including limited sample sizes and inconsistent results. Considering SUA levels as the exposure and CRC as the outcome, the inverse variance-weighted (IVW) approach in MR showed that the odds ratios (ORs) for CRC for each unit increase in SUA were 0.232 (95% confidence interval [CI] of OR 0.094-0.570; P = .001) and 0.551 (95% CI of OR 0.325-0.934; P = .027). Pleiotropic tests and sensitivity analysis confirmed minimal horizontal pleiotropy and the robustness of causality. Our research deepens the understanding of the association between SUA levels and CRC, offering insights into prevention strategies and patient outcomes prediction.

Processing of Shakespearean functional shift as a semantic anomaly in L2 English: Evidence from an ERP study.

Functional shift, a productive word formation in English, converts the functional status of a word without changing its form. A previous event-related potential study reported that functional shift elicited left anterior negativity (LAN) and P600 effects in first language processing, suggesting that shifted words triggered syntactic processes in native English speakers. Using the same materials and experimental methods, this study investigated the processing of functional shift in English as a second language, asking Korean learners of English to make acceptability judgments of sentences containing a functional shift, a semantic incongruity, a double violation, or no violation. The results revealed that functional shift elicited significant N400 effects, indicating that Korean participants processed functionally shifted words as semantic anomalies. Our finding points to the possibility that the mental representation of functional shift differs in L1 and L2.

Mechanistic Insights of Copper Catalyzed Trifluoromethyl Aziridine Opening: Regioselective and Stereospecific Aryl Grignard Addition.

The copper catalyzed regioselective and stereospecific opening of CF3-aziridines is reported. This method focuses on the synthesis of α-CF3-ß-arylethylamines, which can be potential key intermediates in the synthesis of synthetic analogues and biologically active molecules. Density functional theory calculations reveal the nature of the active copper species and the role of the LiClMgX2 (X = Cl or I) as a Lewis acid. Further, the computed mechanism accounts for the high regioselectivity of this transformation.

Luminal androgen receptor subtype and tumor-infiltrating lymphocytes groups based on triple-negative breast cancer molecular subclassification.

In our previous study, we developed a triple-negative breast cancer (TNBC) subtype classification that correlated with the TNBC molecular subclassification. In this study, we aimed to evaluate the predictor variables of this subtype classification on the whole slide and to validate the model's performance by using an external test set. We explored the characteristics of this subtype classification and investigated genomic alterations, including genomic scar signature scores. First, TNBC was classified into the luminal androgen receptor (LAR) and non-luminal androgen receptor (non-LAR) subtypes based on the AR Allred score (≥ 6 and < 6, respectively). Then, the non-LAR subtype was further classified into the lymphocyte-predominant (LP), lymphocyte-intermediate (LI), and lymphocyte-depleted (LD) groups based on stromal tumor-infiltrating lymphocytes (TILs) (< 20%, > 20% but < 60%, and ≥ 60%, respectively). This classification showed fair agreement with the molecular classification in the test set. The LAR subtype was characterized by a high rate of PIK3CA mutation, CD274 (encodes PD-L1) and PDCD1LG2 (encodes PD-L2) deletion, and a low homologous recombination deficiency (HRD) score. The non-LAR LD TIL group was characterized by a high frequency of NOTCH2 and MYC amplification and a high HRD score.

A Case Report of HER2-Amplification in the Breast Without Histological Abnormality.

Atypical ductal hyperplasia and low-grade ductal carcinoma in situ (DCIS) are regarded as precursor lesions of estrogen receptor (ER)-positive invasive breast cancer. In HER2-amplified invasive breast cancer, a precursor lesion before DCIS has not yet been described. Here we introduce a case of HER2-positive lobules in the breast without histological abnormality. A 39-year-old premenopausal woman visited a hospital due to identification of microcalcifications on screening mammography. The subsequent biopsy confirmed high-grade DCIS. She underwent wide excision, and a residual high-grade DCIS with a size of 1.4 cm was found. The tumor cells were hormone receptor positive and HER2 negative on immunohistochemical (IHC) staining. Around DCIS, there were terminal duct lobular units (TDLUs) showing strong HER2 positivity on IHC. These HER2-positive lobules were 7 mm away from the high-grade DCIS and was 1.1 mm in size. These HER2-positive lobules showed no histologic abnormality and had no difference compared with the surrounding normal TDLUs. Nevertheless, in addition to showing HER2 overexpression in IHC, HER2 amplification was also identified in HER2 silver in situ hybridization. HER2 amplification plays an important role in breast cancer development, and HER2 amplification is known to occur as an early event in cancer development. There have been studies identifying driver mutations in normal tissues of other organs. These findings suggest that HER2 amplification in the breast without histological abnormality could occur, and the HER2-positive lobules could be "at risk" for transformation into the precursor lesion of HER2-positive breast cancer, although the biological significance of these findings is unclear.

A Korean male with Kleefstra syndrome presented with micropenis.

Kleefstra syndrome is caused by chromosome 9q34.3 deletion or heterozygous mutations in the euchromatin histone methyl transferase 1 (EHMT1) gene. It can be accompanied by intellectual disability, distinctive facial features, microcephaly, psychiatric disorders, hypotonia in childhood, hearing loss, heart defects, renal defects, epilepsy, speech anomalies, and obesity. Furthermore, genital anomalies are present in 30%-40% of male patients with Kleefstra syndrome, but their mechanisms have not been elucidated. Herein, we report a patient with Kleefstra syndrome presenting with micropenis. The patient was transferred to Kyungpook National University Children's Hospital for management of imperforate anus on the day of birth. Physical examination revealed micropenis with stretched penile length of 0.9 cm and facial dysmorphisms, including hypertelorism and anteverted nares. Chromosomal microarray revealed 424-kb heterozygous deletion at chromosome 9q34.3 (arr[hg19] 9q34.3 (140,234,315-140,659,055)x1). Among the involved main OMIM genes, phenotypically relevant genes were EHMT1 and NSMF. Endocrinological investigation showed low basal gonadotropin and testosterone levels. Anterior pituitary hormones and steroid hormone levels were in the normal range. Testicular function was normal based on human chorionic gonadotropin stimulation test. The patient experienced improvement in penile length growth with intramuscular testosterone enanthate injection initiated at 4 months of age. The purpose of this study is to describe the etiology, endocrine laboratory tests, and treatment of micropenis in Kleefstra syndrome.