Biology subjects

Goldhammer, N.

Publications and source records attributed to Goldhammer, N..

5 recordsLinked to original sources

bioRxiv2026

AutoBlot: deterministic single-cell western blotting reveals proteomic diversity in rare cell populations

Protein abundance and proteoform composition are direct determinants of cellular phenotype, yet both remain difficult to quantify in individual cells from specimens available in limited numbers. Single-cell western blotting (scWB) provides quantitative, molecular-mass-resolved protein measurements but relies on Poisson-limited gravity settling, requiring approximately 10 starting cells while constraining single-cell microwell occupancy to a theoretical maximum of 36.8%. Here, we introduce AutoBlot, an image-guided piezoelectric dispensing approach that deterministically loads individual cells into predefined scWB microwells. AutoBlot achieved approximately 98% single-cell occupancy among targeted microwells while operating from as few as 10,000 starting cells. Across the tested cell concentrations, measured occupancy exceeded Poisson predictions by 31- to 904-fold, and the same dispensing strategy enabled deterministic cell-bead co-loading. We applied AutoBlot to 1,449 cells from seven patient-derived breast organoids generated from histologically normal mammary tissue. Measurements of five lineage-associated proteins revealed donor-to-donor variation, differences associated with germline BRCA1 and menopausal status, and discordance between surface-marker- and cytokeratin-based lineage assignments. AutoBlot also resolved ER-immunoreactive species at approximately 66 and 46 kDa in individual PDO cells. These results establish deterministic cell loading as a strategy for extending molecular-mass-resolved single-cell protein analysis to heterogeneous, cell-limited specimens.

bioengineering↗

bioRxiv2026

Reticulospinal Tract Hyperexcitability in the Upper Limb After Stroke is Associated with Motor Impairment and Not with Functional Compensation

BackgroundAccumulating results suggest that reticulospinal tract (RST) excitability increases after stroke. While animal studies suggest this hyperexcitability may compensate for corticospinal tract (CST) damage, its role in motor function in people with stroke (PwS) remains debated. This study aimed to: (1) replicate findings of RST hyperexcitability in PwS using the StartReact paradigm, measuring acceleration of motor response to a startling auditory stimulus; (2) examine the relationship between RST hyperexcitability and motor impairments after stroke; and (3) explore whether RST hyperexcitability provides functional benefits in severely impaired PwS. MethodsForty-six PwS completed the StartReact paradigm and motor assessments (Fugl-Meyer, ARAT, grip strength, Modified Ashworth Scale). PwS were categorized into high StartReact effect and typical StartReact effect subgroups based on comparisons with a healthy control group (n=37). Severe impairment was defined as ARAT [≤]10. ResultsPwS exhibited significantly greater StartReact effects than controls. The high StartReact effect subgroup showed worse motor function, weaker grip strength, and higher spasticity. Among severely impaired PwS, high StartReact effect was not associated with improved grip strength. ConclusionsThese findings confirm the existence of RST hyperexcitability after stroke and suggest it is associated with poorer motor outcomes, likely due to reduced cortical input to the brainstem. The absence of functional benefit in severely impaired individuals supports the interpretation that RST hyperexcitability is a maladaptive rather than a compensatory reaction to brain damage. These findings provide insight into the neurophysiological mechanisms underlying motor impairments after stroke and do no imply direct clinical or therapeutic applications.

neuroscience↗

bioRxiv2026

Hormone signaling and immune programs define differential endocrine responsiveness in high-risk breast tissue

Hormone therapies are frequently used to reduce breast cancer risk in individuals at increased risk for primary or subsequent disease; however, tissue-level responses to these therapies are heterogeneous and incompletely understood. Background parenchymal enhancement (BPE) on breast magnetic resonance imaging (MRI) provides a non-invasive radiologic readout of breast tissue features associated with endocrine responsiveness and cancer risk. Although BPE is associated with hormonal exposure, a subset of patients with BPE do not show a response to preventive endocrine therapy and therefore may remain at increased breast cancer risk. In this study, we integrated single-nucleus RNA sequencing and spatial transcriptomics to define the determinants of endocrine responsiveness in the setting of BPE. We identify hormone-driven epithelial cells with high levels of estrogen signaling and endocrine responsiveness, together with immune-associated epithelial programs characterized by diminished luminal identity and increased expression of immune-modulatory pathways, including major histocompatibility complex (MHC) class II and CD74. Functional organoid assays validate that these epithelial states exhibit differential sensitivity to tamoxifen and demonstrate that inflammatory signals can induce immune-modulatory epithelial programs. Together, our findings identify hormone signaling and immune programs as key determinants of endocrine responsiveness in breast tissue and provide a biological basis for interpreting radiologic markers relevant to cancer prevention.

cancer biology↗

bioRxiv2025

Joint Mapping of Chromatin Accessibility and Targeted Proteomics in HER2-expressing Breast Cancer Systems

HER2 proteoforms promote therapeutic resistance and aggressiveness in HER2-positive breast cancer, yet their epigenetic consequences remain poorly defined. Here, we establish EpiBlot, a joint assay incorporating a customized plateATAC-seq workflow that minimizes sample inputs with single-cell western blotting to concurrently profile chromatin accessibility with protein and proteoform expression. We applied our method to engineered MCF7 cells expressing HER2 proteoforms - full-length p185HER2 or truncated 611-CTF -, where we evaluated the impact of such proteoforms on the epigenetic and protein profiles after lapatinib or doxorubicin exposure. Expression of 611-CTF elicits pervasive chromatin remodeling, whereas p185HER2 provokes only modest accessibility shifts under the same treatments. EpiBlot reveals that treatment with doxorubicin drives extensive genome-wide accessibility changes, while lapatinib treatment produces limited global effects but unmasks proteoform-specific responses. Concordance between chromatin accessibility and protein abundance is moderate, underscoring complex regulatory coupling. Extending this dual-modality approach to HER2-low patient-derived organoids uncovers distinct chromatin states and reveals a subpopulation of triple-negative breast-cancer cells expressing truncated HER2 proteoforms. We anticipate that EpiBlot will highlight the value of multimodal profiling with proteoform identification for dissecting tumor heterogeneity and therapeutic response in cancer. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=198 SRC="FIGDIR/small/678463v2_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@673263org.highwire.dtl.DTLVardef@11d28c5org.highwire.dtl.DTLVardef@15fa336org.highwire.dtl.DTLVardef@1d4426b_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2025

Fine needle aspiration biopsy of breast specimens effectively harvests cells for patient-derived organoids modeling breast ductal carcinoma in situ

BackgroundPatient-derived organoids (PDOs) generated from benign breast tissue and breast carcinomas have successfully recapitulated their respective in vivo counterparts. PDOs model tumorigenesis and allow for screening of novel therapeutics personalized to individual patients. However, acquiring cells to generate PDOs is cumbersome. We demonstrate the feasibility of fine needle aspiration biopsy (FNAB) for harvesting cells for PDOs modeling ductal carcinoma in situ (DCIS). MethodsSurgical specimens from patients with biopsy-proven DCIS were used for this study. Core needle biopsy (CNB) was performed on fresh specimens in the operating room, and tissue was mechanically dissociated before culture in basement membrane extract (BME) and organoid medium to generate PDOs. FNAB was performed in the gross room on fresh specimens, and the remaining aspirate was similarly submitted for PDO culture. ResultsPDOs were successfully generated in 15/18 specimens obtained by CNB and 7/11 specimens obtained by FNAB. The average time to initial organoid growth was 4 days for FNAB specimens compared to 19.3 days for CNB specimens. Tumor cells were seen on 7/11 FNAB smears and 16/18 CNB touch preps. Immunofluorescence staining confirmed the presence of both luminal and myoepithelial cells in derived PDOs. ConclusionsFNAB effectively obtains cells for PDOs modeling DCIS. CNB after mincing yielded PDOs with a high success rate, but they were slow to establish. Notably, the time to organoid growth was significantly shorter for FNAB specimens. Thus, FNAB offers an efficient alternative for breast PDO culture and can reduce the time and resources spent on generating PDO cultures.

cell biology↗