Faculty Bibliography

The superior aesthetic outcomes of nipple-sparing mastectomies (NSM) explain their increased use and rising popularity. Fortunately, cancer recurrences involving the nipple-areolar complex (NAC) have been reassuringly low in the range of 1%. Technical considerations and challenges of this procedure are centered on nipple ischemia and necrosis. Patient selection, reconstructive strategies and incision placement have lowered ischemic complications. In this context, rates of full NAC necrosis are 3% or less. The emergence of noninvasive tissue angiography provides surgeons with a practical tool to assess real-time breast skin and NAC perfusion. Herein, we review our classification system of NAC perfusion patterns defined as V1 (from subjacent breast), V2 (surrounding skin), and V3 (combination of V1 + V2). Additionally, we describe the benefits of a first stage operation to devascularize the NAC as a means of improving blood flow to the NAC in preparation for NSM, helping extend the use of NSM to more women. Intraoperative evaluation of skin perfusion allows surgeons to detect ischemia and modify the operative approach to optimize outcomes.

The regulation of organ size is essential to human health and has fascinated biologists for centuries. Key to the growth process is the ability of most organs to integrate organ-extrinsic cues (eg, nutritional status, inflammatory processes) with organ-intrinsic information (eg, genetic programs, local signals) into a growth response that adapts to changing environmental conditions and ensures that the size of an organ is coordinated with the rest of the body. Paired organs such as the vertebrate limbs and the long bones within them are excellent models for studying this type of regulation because it is possible to manipulate one member of the pair and leave the other as an internal control. During development, growth plates at the end of each long bone produce a transient cartilage model that is progressively replaced by bone. Here, we review how proliferation and differentiation of cells within each growth plate are tightly controlled mainly by growth plate-intrinsic mechanisms that are additionally modulated by extrinsic signals. We also discuss the involvement of several signaling hubs in the integration and modulation of growth-related signals and how they could confer remarkable plasticity to the growth plate. Indeed, long bones have a significant ability for "catch-up growth" to attain normal size after a transient growth delay. We propose that the characterization of catch-up growth, in light of recent advances in physiology and cell biology, will provide long sought clues into the molecular mechanisms that underlie organ growth regulation. Importantly, catch-up growth early in life is commonly associated with metabolic disorders in adulthood, and this association is not completely understood. Further elucidation of the molecules and cellular interactions that influence organ size coordination should allow development of novel therapies for human growth disorders that are noninvasive and have minimal side effects.

Background: GWAS studies in schizophrenia have not yielded targets for person-specific interventions. Alternatively, studies can focus on genes that were initially identified as harboring disruptive de novo mutations in sporadic cases. We examined the impact of four such genes on illness phenotypes. Methods: Structured interviews (DIGS), cognition (WAIS III), symptoms (PANSS) were examined in 48 genotyped cases finding that over 30% of the sample carried a rare/ missense mutations in any of 4 genes. Gene carrier groups were compared to cases without any of these mutations and healthy controls. Results: Carriers of disrupted genes showed significant differences, as follows: SLC39A13 (zinc transporter) (n=4) had the greatest psychopathology and severe cognitive deficits; TGM5 (n=4) had fewer symptoms but slower processing speed; PTPRG (n=5) had prematurity, childhood psychosis and good cognition except poor working memory; ARMS/KIDINS220 (n=5) had comparable severe pathology in all symptom factors and cognitive scores, though degeneration is suggested in light of their early accomplishments. Individual case vignettes highlighted familial psychosis, learning disorders, substance abuse, traumatic brain injuries and medical comorbidity in all 4 subgroups. Conclusions: The results suggest that genes prone to de novo mutations in sporadic cases may provide missing leverage to resolve the complexity of schizophrenia. A differential focus on working memory, processing speed, neuroprotection and zinc treatment should be pursued for these newly identified conditions. Other findings are that ethnicity may not limit genetic research when the focus is on gene function rather than particular sequence variations, and that premorbid exposures may sometimes reflect pleiotrophic effects of psychosis vulnerability genes rather than exposures producing nongenetic phenocopies. This novel approach may be applicable to other complex disorders

Vertebrate centrioles normally propagate through duplication, but in the absence of preexisting centrioles, de novo synthesis can occur. Consistently, centriole formation is thought to strictly rely on self-assembly, involving self-oligomerization of the centriolar protein SAS-6. Here, through reconstitution of de novo synthesis in human cells, we surprisingly found that normal looking centrioles capable of duplication and ciliation can arise in the absence of SAS-6 self-oligomerization. Moreover, whereas canonically duplicated centrioles always form correctly, de novo centrioles are prone to structural errors, even in the presence of SAS-6 self-oligomerization. These results indicate that centriole biogenesis does not strictly depend on SAS-6 self-assembly, and may require preexisting centrioles to ensure structural accuracy, fundamentally deviating from the current paradigm.

The presenilin 1 (PSEN1) L271V mutation causes early-onset familial Alzheimer's disease by disrupting the alternative splicing of the PSEN1 gene, producing some transcripts harboring the L271V point mutation and other transcripts lacking exon 8 (PS1exon8). We previously reported that PS1 L271V increased amyloid beta (Abeta) 42/40 ratios, while PS1exon8 reduced Abeta42/40 ratios, indicating that the former and not the exon 8 deletion transcript is amyloidogenic. Also, PS1exon8 did not rescue Abeta generation in PS1/2 double knockout cells indicating its identity as a severe loss-of-function splice form. PS1exon8 is generated physiologically raising the possibility that we had identified the first physiological inactive PS1 isoform. We studied PS1exon8 in vivo by crossing PS1exon8 transgenics with either PS1-null or Dutch APPE693Q mice. As a control, we crossed APPE693Q with mice expressing a deletion in an adjacent exon (PS1exon9). PS1exon8 did not rescue embryonic lethality or Notch-deficient phenotypes of PS1-null mice displaying severe loss of function in vivo. We also demonstrate that this splice form can interact with wildtype PS1 using cultured cells and co-immunoprecipitation (co-IP)/bimolecular fluorescence complementation. Further co-IP demonstrates that PS1exon8 interacts with nicastrin, participating in the gamma-secretase complex formation. These data support that catalytically inactive PS1exon8 is generated physiologically and participates in protein-protein interactions.

Avoiding temperatures outside the physiological range is critical for animal survival, but how temperature dynamics are transformed into behavioral output is largely not understood. Here, we used an infrared laser to challenge freely swimming larval zebrafish with "white-noise" heat stimuli and built quantitative models relating external sensory information and internal state to behavioral output. These models revealed that larval zebrafish integrate temperature information over a time-window of 400 ms preceding a swimbout and that swimming is suppressed right after the end of a bout. Our results suggest that larval zebrafish compute both an integral and a derivative across heat in time to guide their next movement. Our models put important constraints on the type of computations that occur in the nervous system and reveal principles of how somatosensory temperature information is processed to guide behavioral decisions such as sensitivity to both absolute levels and changes in stimulation.

The yeast homologs of the ATM and ATR DNA damage response kinases play key roles in telomerase-mediated telomere maintenance, but the role of ATM/ATR in the mammalian telomerase pathway has been less clear. Here, we demonstrate the requirement for ATM and ATR in the localization of telomerase to telomeres and telomere elongation in immortal human cells. Stalled replication forks increased telomerase recruitment in an ATR-dependent manner. Furthermore, increased telomerase recruitment was observed upon phosphorylation of the shelterin component TRF1 at an ATM/ATR target site (S367). This phosphorylation leads to loss of TRF1 from telomeres and may therefore increase replication fork stalling. ATM and ATR depletion reduced assembly of the telomerase complex, and ATM was required for telomere elongation in cells expressing POT1DeltaOB, an allele of POT1 that disrupts telomere-length homeostasis. These data establish that human telomerase recruitment and telomere elongation are modulated by DNA-damage-transducing kinases.

The mechanisms by which mutations in FUS and other RNA binding proteins cause ALS and FTD remain controversial. We propose a model in which low-complexity (LC) domains of FUS drive its physiologically reversible assembly into membrane-free, liquid droplet and hydrogel-like structures. ALS/FTD mutations in LC or non-LC domains induce further phase transition into poorly soluble fibrillar hydrogels distinct from conventional amyloids. These assemblies are necessary and sufficient for neurotoxicity in a C. elegans model of FUS-dependent neurodegeneration. They trap other ribonucleoprotein (RNP) granule components and disrupt RNP granule function. One consequence is impairment of new protein synthesis by cytoplasmic RNP granules in axon terminals, where RNP granules regulate local RNA metabolism and translation. Nuclear FUS granules may be similarly affected. Inhibiting formation of these fibrillar hydrogel assemblies mitigates neurotoxicity and suggests a potential therapeutic strategy that may also be applicable to ALS/FTD associated with mutations in other RNA binding proteins.

Modulation of Toll-like receptor (TLR) signaling can have protective or protumorigenic effects on oncogenesis depending on the cancer subtype and on specific inflammatory elements within the tumor milieu. We found that TLR9 is widely expressed early during the course of pancreatic transformation and that TLR9 ligands are ubiquitous within the tumor microenvironment. TLR9 ligation markedly accelerates oncogenesis, whereas TLR9 deletion is protective. We show that TLR9 activation has distinct effects on the epithelial, inflammatory, and fibrogenic cellular subsets in pancreatic carcinoma and plays a central role in cross talk between these compartments. Specifically, TLR9 activation can induce proinflammatory signaling in transformed epithelial cells, but does not elicit oncogene expression or cancer cell proliferation. Conversely, TLR9 ligation induces pancreatic stellate cells (PSCs) to become fibrogenic and secrete chemokines that promote epithelial cell proliferation. TLR9-activated PSCs mediate their protumorigenic effects on the epithelial compartment via CCL11. Additionally, TLR9 has immune-suppressive effects in the tumor microenvironment (TME) via induction of regulatory T cell recruitment and myeloid-derived suppressor cell proliferation. Collectively, our work shows that TLR9 has protumorigenic effects in pancreatic carcinoma which are distinct from its influence in extrapancreatic malignancies and from the mechanistic effects of other TLRs on pancreatic oncogenesis.

The C. elegans germ line is an outstanding model system to study the control of cell division and differentiation. While many of the molecules that regulate germ cell proliferation and fate decisions have been identified, how these signals interact with cellular dynamics and physical forces within the gonad remains poorly understood. We therefore developed a dynamic, 3D in silico model of the C. elegans germ line, incorporating both the mechanical interactions between cells and the decision-making processes within cells. Our model successfully reproduces key features of the germ line during development and adulthood, including a reasonable ovulation rate, correct sperm count, and appropriate organization of the germ line into stably maintained zones. The model highlights a previously overlooked way in which germ cell pressure may influence gonadogenesis, and also predicts that adult germ cells may be subject to mechanical feedback on the cell cycle akin to contact inhibition. We provide experimental data consistent with the latter hypothesis. Finally, we present cell trajectories and ancestry recorded over the course of a simulation. The novel approaches and software described here link mechanics and cellular decision-making, and are applicable to modeling other developmental and stem cell systems.